Electrophoretic dispersion liquid, method of manufacturing electrophoretic dispersion liquid, electrophoretic sheet, electrophoretic device, and electronic apparatus

ABSTRACT

According to the invention, an electrophoretic dispersion liquid includes at least one type of an electrophoretic particle, and a dispersion medium, in which the content of transition metal of group 8 elements derived from a catalyst which is used to generate at least one of a block copolymer (a particle surface treatment agent) used to form the electrophoretic particle and the dispersion medium is in a range of greater than 0 ppm to equal to or less than 2 ppm in the electrophoretic dispersion liquid.

BACKGROUND

1. Technical Field

The present invention relates to an electrophoretic dispersion liquid, amethod of manufacturing an electrophoretic dispersion liquid, anelectrophoretic sheet, an electrophoretic device, and an electronicapparatus.

2. Related Art

Generally, the fact that when an electric field is applied to a dispersesystem in which fine particles are dispersed in a fluid, the fineparticles move (migrate) in the fluid by Coulomb's force has been known.This phenomenon is called electrophoresis, and recently, anelectrophoretic display device which displays desired information (animage) by using the electrophoresis has attracted attention as a newdisplay device.

Such an electrophoretic display device has display memory properties andwide viewing angle properties in a state of stopping the application ofvoltage, and is capable of performing high contrast display and lowpower consumption.

In addition, the electrophoretic display device is a non light-emittingtype device, and thus is easy on the eyes as compared with alight-emitting type display device such as a cathode-ray tube.

It has been known that such an electrophoretic display device includes aliquid which disperses the electrophoretic particles in a dispersionmedium as the electrophoretic dispersion liquid disposed between a pairof substrates having electrodes.

In the electrophoretic dispersion liquid of the above-describedconfiguration, a positively charged particle and a negatively chargedparticle are used as the electrophoretic particle, and thus it ispossible to display desired information (image) by applying a voltageacross a pair of substrates (electrodes).

As the aforementioned electrophoretic particle, typically, a particlehaving a coated layer in which a polymer is bonded to a base materialparticle is used, and with such a configuration of having the coatedlayer (polymer), it is possible to disperse and charge theelectrophoretic particles in the electrophoretic dispersion liquid(refer to JP-A-2005-241784).

In the above-described electrophoretic dispersion liquid, as a method ofimproving dispersibility of the electrophoretic particle, for example, amethod of setting a polymer and a dispersion medium which are containedin the electrophoretic particle to contain a siloxane-based compound,and of improving the affinity therebetween is considered.

When the siloxane-based compound is used, a catalyst is used at the timeof generating the siloxane-based compound, and the transition metal ofgroup 8 elements such as Pt may be contained in the catalyst. For thisreason, the transition metal of group 8 elements used to generate thesiloxane-based compound involuntarily remains in the electrophoreticdispersion liquid, and as a result, due to the remaining transitionmetal of group 8 elements, the dispersibility of the electrophoreticparticles in the electrophoretic dispersion liquid is not improved to adesired degree, which is a problem.

SUMMARY

An advantage of some aspects of the invention is to provide anelectrophoretic dispersion liquid in which an electrophoretic particleexhibits both excellent dispersion ability and electrophoreticproperties, a method of manufacturing the electrophoretic dispersionliquid, an electrophoretic sheet, an electrophoretic device, and anelectronic apparatus which use the electrophoretic dispersion liquid andthus has high reliability.

Such an advantage can be achieved in the following aspects of theinvention.

According to an aspect of the invention, there is provided anelectrophoretic dispersion liquid including at least one type ofelectrophoretic particles and a dispersion medium, in which the contentof transition metal of group 8 elements is in a range of greater than 0ppm to equal to or less than 2 ppm in the electrophoretic dispersionliquid.

With this, it is possible to realize the electrophoretic dispersionliquid containing the electrophoretic particle with excellent dispersionability and electrophoretic properties.

In the electrophoretic dispersion liquid of the invention, it ispreferable that the transition metal of group 8 elements is derived froma catalyst which is used to generate at least one of a particle surfacetreatment agent used to form the electrophoretic particle and adispersant added to the dispersion medium.

The transition metal of group 8 element which is derived from thecatalyst which is used to generate at least one of the particle surfacetreatment agent used to form the electrophoretic particle and thedispersant added to the dispersion medium remains in the electrophoreticdispersion liquid.

In the electrophoretic dispersion liquid of the invention, it ispreferable that the transition metal of group 8 element is at least oneof a period 5 element and a period 6 element.

The catalyst containing the transition metal of group 8 element of theperiod 5 element and the period 6 element can be used to generate theparticle surface treatment agent and the dispersion medium. For thisreason, it is possible to reliably improve the dispersibility of theelectrophoretic particle by setting the content of the metal elements tobe in a range of greater than 0 ppm to equal to or less than 2 ppm inthe electrophoretic dispersion liquid.

In the electrophoretic dispersion liquid of the invention, it ispreferable that in the electrophoretic dispersion liquid, the transitionmetal of group 8 element is present in a state where at least one of acomplex and salt which contain the transition metal of group 8 elementis formed.

As such, even in a case where the transition metal of group 8 element iscontained in the electrophoretic dispersion liquid in a state where boththe complex and salt are formed, it is possible to reliably improve thedispersibility of the electrophoretic particle by setting the content ofthe transition metal of group 8 elements to be in a range of greaterthan 0 ppm to equal to or less than 2 ppm in the electrophoreticdispersion liquid.

In the electrophoretic dispersion liquid of the invention, it ispreferable that at least one of the particle surface treatment agent andthe dispersant is a siloxane-based compound.

As described above, in a case where at least one of the particle surfacetreatment agent and the dispersion medium is the siloxane-basedcompound, with the application of the invention, it is possible toimprove the dispersibility of the electrophoretic particle in theelectrophoretic dispersion liquid by setting the content of thetransition metal of group 8 elements to be in a range of greater than 0ppm to equal to or less than 2 ppm in the electrophoretic dispersionliquid.

In the electrophoretic dispersion liquid of the invention, it ispreferable that the siloxane-based compound is a polymer compound.

At the time of obtaining such a siloxane-based compound which is apolymer compound, the catalyst containing the transition metal of group8 element is used, and thus it is possible to improve the dispersibilityof the electrophoretic particle in the electrophoretic dispersion liquidby setting the content of the transition metal of group 8 elements to bein a range of greater than 0 ppm to equal to or less than 2 ppm in theelectrophoretic dispersion liquid.

In the electrophoretic dispersion liquid of the invention, it ispreferable that the siloxane-based compound which is used as theparticle surface treatment agent is a block copolymer which contains adispersion portion which is formed by polymerizing first monomers and abonding portion which is formed by polymerizing second monomers having afunctional group, and is bonded to the electrophoretic particle when thefunctional group and a hydroxyl group are reacted with each other in thebonding portion, and the first monomer is a silicone macromonomerexpressed by the following Formula (I).

[In the formula, R¹ represents a hydrogen atom or a methyl group, R²represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms,R³ represents a structure including one of an alkyl group having 1 to 6carbon atoms and an ether group of ethylene oxide or propylene oxide,and n represents an integer of 0 or greater.]

At the time of obtaining the silicone macromonomer expressed by Formula(I), the catalyst containing the transition metal of group 8 element isused, and thus it is possible to improve the dispersibility of theelectrophoretic particle in the electrophoretic dispersion liquid bysetting the content of the transition metal of group 8 elements to be ina range of greater than 0 ppm to equal to or less than 2 ppm in theelectrophoretic dispersion liquid.

In the electrophoretic dispersion liquid of the invention, it ispreferable that the siloxane-based compound used as the dispersant is amodified silicone compound.

As described above, when the modified silicone compound is used as thedispersant, the catalyst containing the transition metal of group 8element may be used to generate the modified silicone compound, and thusit is possible to improve the dispersibility of the electrophoreticparticle in the electrophoretic dispersion liquid by setting the contentof the transition metal of group 8 elements to be in a range of greaterthan 0 ppm to equal to or less than 2 ppm in the electrophoreticdispersion liquid.

According to another aspect of the invention, there is provided a methodof manufacturing an electrophoretic dispersion liquid which includes atleast one type of an electrophoretic particle, and a dispersion medium,the method including: generating a particle surface treatment agentwhich is used to form the electrophoretic particle by using a catalyst;removing the transition metal of group 8 element which is derived fromthe catalyst from the particle surface treatment agent; bonding theparticle surface treatment agent onto a surface of a base particle so asto obtain the electrophoretic particle; and dispersing theelectrophoretic particles in the dispersion medium so as to obtain theelectrophoretic dispersion liquid in which the content of the transitionmetal of group 8 elements derived from the catalyst is in a range ofgreater than 0 ppm to equal to or less than 2 ppm.

With this, it is possible to manufacture the electrophoretic dispersionliquid containing the electrophoretic particle with the excellentdispersion ability and electrophoretic properties.

According to still another aspect of the invention, there is provided amethod of manufacturing an electrophoretic dispersion liquid whichincludes at least one type of an electrophoretic particle, and adispersion medium, the method including: generating a dispersant whichis added in the dispersion medium by using a catalyst; removingtransition metal of group 8 elements which is derived from the catalystfrom the dispersant; and dispersing the electrophoretic particles in thedispersion medium containing the dispersant so as to obtain theelectrophoretic dispersion liquid in which the content of the transitionmetal of group 8 elements derived from the catalyst is in a range ofgreater than 0 ppm to equal to or less than 2 ppm.

With this, it is possible to manufacture the electrophoretic dispersionliquid containing the electrophoretic particle with the excellentdispersion ability and electrophoretic properties.

In the method of manufacturing an electrophoretic dispersion liquid ofthe invention, it is preferable that in the removing, a method ofremoving the transition metal of group 8 elements from the particlesurface treatment agent or the dispersant is at least one of acentrifugation method performed by centrifugation of the transitionmetal of group 8 elements, an adsorption method performed by adsorbingthe transition metal of group 8 elements into an adsorbent, and anextracting method performed in such a manner that a water-soluble metalcomplex containing the transition metal of group 8 elements is formedand phase-separated, and then extracted.

According to the above-described methods, it is possible to remove thetransition metal of group 8 elements from at least one of the particlesurface treatment agent and the dispersion medium, with an excellentremoval rate.

According to still another aspect of the invention, there is provided anelectrophoretic sheet including a substrate; and a structure body whichis provided on the substrate, and accommodates the electrophoreticdispersion liquid of the invention.

With this, it is possible to obtain the electrophoretic sheet withhigh-performance and reliability.

According to still another aspect of the invention, there is provided anelectrophoretic device including the electrophoretic sheet of theinvention.

With this, it is possible to obtain the electrophoretic device withhigh-performance and reliability.

According to still another aspect of the invention, there is provided anelectronic apparatus including the electrophoretic device of theinvention.

With this, it is possible to obtain the electronic apparatus withhigh-performance and reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a longitudinal sectional view illustrating a first embodimentof an electrophoretic particle contained in an electrophoreticdispersion liquid of the invention.

FIG. 2 is a schematic diagram of a block copolymer contained in theelectrophoretic particle illustrated in FIG. 1.

FIG. 3 is a longitudinal sectional view illustrating a second embodimentof an electrophoretic particle contained in an electrophoreticdispersion liquid of the invention.

FIG. 4 is a diagram illustrating a siloxane-based coupling agent whichis bonded onto a surface of a base particle of the electrophoreticparticle illustrated in FIG. 3.

FIG. 5 is a diagram illustrating, regarding a coupling agent and amodified silicone oil which are used to obtain the siloxane-basedcoupling agent having a structure Z illustrated in FIG. 4, specificexamples of a reactive functional group X contained in the couplingagent, and a reactive functional group Y contained in the modifiedsilicone oil.

FIG. 6A to FIG. 6F are diagrams illustrating a polarization group whichis bonded onto the surface of the electrophoretic particle illustratedin FIG. 3.

FIG. 7 is a diagram for schematically illustrating a longitudinal crosssection of the electrophoretic display device of the embodiment.

FIG. 8A and FIG. 8B are schematic diagrams illustrating an operatingprinciple of the electrophoretic display device illustrated in FIG. 7.

FIG. 9 is a perspective view illustrating an embodiment in a case wherean electronic apparatus of the invention is applied to an electronicpaper.

FIG. 10A and FIG. 10B are diagrams illustrating an embodiment in a casewhere the electronic apparatus of the invention is applied to a display.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, preferable embodiments of an electrophoretic dispersionliquid, a method of manufacturing an electrophoretic dispersion liquid,an electrophoretic sheet, an electrophoretic device, and an electronicapparatus of the invention will be specifically described with referenceto the drawings.

Electrophoretic Dispersion Liquid First Embodiment

The electrophoretic dispersion liquid contains at least one type ofelectrophoretic particles 1, and a dispersion medium (a liquid phasedispersion medium), and in the electrophoretic dispersion liquid, theelectrophoretic particles 1 are dispersed (suspended) in the dispersionmedium.

First, the electrophoretic particles 1 contained in the electrophoreticdispersion liquid will be described.

Electrophoretic Particle

FIG. 1 is a longitudinal sectional view illustrating a first embodimentof the electrophoretic particle contained in an electrophoreticdispersion liquid of the invention, and FIG. 2 is a schematic diagram ofa block copolymer contained in the electrophoretic particle illustratedin FIG. 1.

As illustrated in FIG. 1, the electrophoretic particle 1 includes a baseparticle (particle) 2 and a coated layer 3 provided on a surface of thebase particle 2.

As the base particle 2, for example, at least one of a pigment particle,a resin particle, and a composite particle thereof is preferably used.These particles are easily manufactured.

Examples of the pigment for constituting the pigment particle include ablack pigment such as aniline black, carbon black, and titanium black, awhite pigment such as titanium dioxide, antimony trioxide, bariumsulfate, zinc sulfide, zinc oxide, and silicon dioxide, an azo-basedpigment such as monoazo, disazo, and polyazo, a yellow pigment such asisoindolinone, chrome yellow, yellow iron oxide, cadmium yellow,titanium yellow, and antimony, a red pigment such as quinacridone redand chrome vermilion, a blue pigment such as phthalocyanine blue,indanthrene blue, Prussian blue, ultramarine blue, and cobalt blue, anda green pigment such as phthalocyanine green. These pigments may be usedalone or in combination of two or more types thereof.

In addition, examples of a resin material for constituting resinparticles include an acrylic resin, a urethane resin, a urea resin, anepoxy resin, polystyrene, and polyester. These resins may be used aloneor in combination of two or more types thereof.

In addition, examples of the composite particle include a particleobtained by performing a coating treatment in which the surface of thepigment particle is coated with the resin material, a particle obtainedby performing a coating treatment in which the surface of the resinparticle is coated with the pigment, and a particle composed of amixture obtained by mixing the pigment and the resin material at anappropriate composition ratio.

Meanwhile, it is possible to set a desired color for the electrophoreticparticle 1 by appropriately selecting the type of the pigment particle,the resin particle, and the composite particle which are used as thebase particle 2.

In addition, due to the above selection, the positive chargingproperties or the negative charging properties of the base particle 2,and the charging amount thereof can be set as a unique matter of thebase particle 2.

Note that, it is necessary that the base particle 2 includes (exposes) afirst functional group which can be bonded to (react with) a secondfunctional group included in a bonding portion 31 of a block copolymer39 described below on the surface thereof. However, there is a casewhere the base particle 2 does not include a functional group dependingon the type of the pigment particle, the resin particle, and thecomposite particle, and thus, in this case, the first functional groupis introduced to the surface of the base particle 2 by performing inadvance a functional group introduction treatment such as an acidtreatment, a base treatment, a UV treatment, an ozone treatment, and aplasma treatment.

Meanwhile, the combination of the first functional group which isprovided on the surface of the base particle 2, and the secondfunctional group which includes the bonding portion 31 of the blockcopolymer 39 is not particularly limited as long as the materials can bebonded to each other through the reaction therebetween. For example,examples of the combination include a combination of an isocyanate groupand a hydroxyl group or an amino group, a combination of an epoxy group,a glycidyl group or an oxetane group and a carboxyl group, an aminogroup, a thiol group, and a hydroxyl group or an imidazole group, acombination of an amino group and a halogen group such as Cl, Br, and I,and a combination of an alkoxysilyl group and a hydroxyl group or analkoxysilyl group. Among them, a combination of the hydroxyl group asthe first functional group and the alkoxysilyl group as the secondfunctional group is preferably used.

Both of the base particle 2 having the above combination and a monomerM2 can be relatively easily prepared, and are preferably used since themonomer M2 (a block copolymer described below) can be firmly bonded ontothe surface of the base particle 2.

Hereinafter, an example of a combination of the first functional groupwhich is provided on the surface of the base particle 2 as a hydroxylgroup with the second functional group provided in the monomer M2 as analkoxysilyl group will be described.

In the base particle 2, at least a portion (almost the entire surface inthe configuration in the drawing) of the surface thereof is coated withthe coated layer 3.

The coated layer 3 is configured to include a plurality of the blockcopolymers 39 (hereinafter, simply referred to as a “polymer 39”) (referto FIG. 2).

The block copolymer 39 includes a dispersion portion 32 and the bondingportion 31 which is bonded to the dispersion portion 32, and thedispersion portion 32 is formed by polymerizing first monomers M1(hereinafter, simply referred to as a “monomer M1”) having a portion (agroup) for contributing to the dispersibility in the dispersion medium,and includes a plurality of units (constituting units, hereinafter,referred to as a dispersion unit) derived from the monomer M1. Thebonding portion 31 is formed by polymerizing second monomers M2 of whichhave an alkoxysilyl group (the second functional group) and is reactedwith a hydroxyl group (the first functional group) on the surface of thebase particle, and includes a plurality of units (hereinafter, referredto as a “bonding unit”) derived from the monomers M2. In the bondingportion 31, when the hydroxyl group and the functional group are reactedwith each other, the base particle 2 and the block copolymer 39 arechemically bonded.

In the embodiment, the aforementioned block copolymer 39 forms aparticle surface treatment agent which is used to form theelectrophoretic particle 1.

Hereinafter, the dispersion portion 32 and the bonding portion 31 whichform the aforementioned block copolymer 39 will be described below.

The dispersion portion 32 is provided on the surface of the baseparticle 2 in the coated layer 3 so as to impart the dispersibility tothe electrophoretic particle 1 in the electrophoretic dispersion liquid.

In the electrophoretic dispersion liquid, the aforementioned dispersionportion 32 is formed by polymerizing the plurality of monomers M1 whichinclude a portion that becomes a side chain for contributing to thedispersibility in the dispersion medium after being polymerized, andincludes the plurality of dispersion units derived from the monomers M1,which are bonded to each other.

Each of the monomers M1 has one polymerizable group such that themonomers M1 are polymerized by the living radical polymerization (theradical polymerization), and is a pendant-type monofunctional monomerwhich includes a portion corresponding to a non-ionic side chain afterperforming polymerization.

In the embodiment, a silicone macromonomer expressed by the followingFormula (I) which has dimethyl polysiloxane as the non-ionic side chain,and a (meth)acryloyl group as the polymerizable group is used as themonomer M1.

[In the formula, R¹ represents a hydrogen atom or a methyl group, R²represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms,R³ represents a structure including one of an alkyl group having 1 to 6carbon atoms and an ether group of ethylene oxide or propylene oxide,and n represents an integer of 0 or greater.]

When the silicone macromonomer having such a non-ionic side chain isused as the monomer M1, the dispersion portion 32 which is formed by theliving radical polymerization exhibits excellent affinity with respectto a silicone oil used as a dispersion medium which is included in theelectrophoretic dispersion liquid described below. For this reason, theelectrophoretic particles 1 which include the dispersion portion 32 aredispersed with excellent dispersibility in the electrophoreticdispersion liquid without being aggregated. In addition, when themonomer M1 having the (meth)acryloyl group as the polymerizable group isused, the monomers M1 can be polymerized with each other with excellentreactivity, and thus it is possible to easily obtain the dispersionportion 32.

The weight-average molecular weight of the silicone macromonomerexpressed by Formula (I) above as the monomer M1 is preferably in arange of approximately 1,000 to 50,000, is further preferably in a rangeof approximately 3,000 to 30,000, and is still further preferably in arange of approximately 5,000 to 20,000. With this, it is possible todisperse the electrophoretic particles 1 which include the dispersionportion 32 obtained by polymerizing the monomers M1 in the dispersionmedium with further excellent dispersibility.

In addition, the weight-average molecular weight of the dispersionportion 32 is not particularly limited, but is preferably in a range of8,000 to 50,000, and is further preferably in a range of 10,000 to35,000. With this, it is possible to make the dispersibility of theelectrophoretic particle 1 in the electrophoretic dispersion liquidfurther excellent.

Further, in one polymer, the number of the dispersion units included inthe dispersion portion 32 is preferably in a range of 1 to 20, and isfurther preferably in a range of 2 to 10. With this, it is possible toreliably impart the dispersibility of the electrophoretic particle 1 inthe electrophoretic dispersion liquid.

In addition, the molecular weight distribution of the dispersion portion32 is preferably equal to or lower than 1.2, is further preferably equalto or lower than 1.1, and is still further preferably equal to or lowerthan 1.05.

Here, the molecular weight distribution of the dispersion portion 32represents the ratio (Mw/Mn) of the number average molecular weight (Mn)of the dispersion portion 32 to the weight-average molecular weight (Mw)of the dispersion portion 32, and it can be said that when the molecularweight distribution of the dispersion portion 32 is within theabove-described range, the dispersion portions 32 which are exposed inthe plurality of electrophoretic particles 1 have almost the samelength. For this reason, in the electrophoretic dispersion liquid, eachof the electrophoretic particles 1 exhibits uniform dispersion ability.The above-described number average molecular weight (Mn) and theweight-average molecular weight (Mw) can be measured as molecular weightin terms of polystyrene by using, for example, a gel permeationchromatography (GPC) method.

Further, in the dispersion portion 32, the molecular weight of thedispersion unit of the proximal end portion side which is bonded to thebonding portion 31 is preferably smaller than the molecular weight ofthe dispersion unit of the distal end portion side. More specifically,the molecular weight of the side chain which is included in the monomerM1 corresponding to a precursor of the dispersion unit positioned on theproximal end portion side is preferably smaller than the molecularweight of the side chain which is included in the monomer M1corresponding to the precursor of the dispersion unit positioned on thedistal end portion side. With this, it is possible to make furtherexcellent dispersibility of the electrophoretic particle 1 in theelectrophoretic dispersion liquid, and to bond the dispersion portion 32onto the surface of the base particle 2 with high density.

In addition, a change of molecular weight of the side chain may becomecontinuously larger to the proximal end side from the distal end side,or may become gradually larger to the proximal end side from the distalend side.

The bonding portion 31 is bonded onto the surface of the base particle 2in the coated layer 3 provided in the electrophoretic particle 1. Withthis, the polymer 39 is bonded to the base particle 2.

In the embodiment, the bonding portion 31 is formed by polymerizing theplurality of second monomers M2 formed on the surface of the baseparticle 2, each of which is reacted with a hydroxyl group so as to becovalently bonded, and has the second functional group, and includes theplurality of bonding units (constituting units) derived from themonomers M2 which are arranged therein.

As such, it is possible to make further excellent dispersibility of theelectrophoretic particles 1 by using the polymer 39 including thebonding portion 31 which has the plurality of bonding units of which hasa functional group. That is, the polymer 39 has a plurality of thefunctional groups, and the plurality of functional groups areconcentrically present in the bonding portion 31. Further, the bondingportion 31 is bonded to the plurality of bonding units, and thus has alarge portion which can be reacted with the base particle 2 as comparedwith a case where only one bonding unit is present. For this reason, itis possible to reliably bond the polymer 39 onto the surface of the baseparticle 2 in the bonding portion 31 which is formed by polymerizing theplurality of monomers M2.

In addition, in the embodiment, the hydroxyl group is included on thesurface of the base particle 2, and the functional group included in themonomer M2 is the alkoxysilyl group, as described above. When thehydroxyl group and the alkoxysilyl group are combined with each other,the reaction therebetween exhibits the excellent reactivity, and thus itis possible to reliably bond the polymer 39 onto the surface of the baseparticle 2 in the bonding portion 31.

Such a monomer M2 includes one alkoxysilyl group expressed by thefollowing Formula (II) as a functional group, and one polymerizablegroup such that the polymerization is performed by the living radicalpolymerization.

[In the formula, each of R's independently represents an alkyl grouphaving 1 to 4 carbon atoms, and n represents an integer of 1 to 3.]

When the above-described configuration is used as the monomer M2, it ispossible to form the bonding portion 31 in which the monomers M2 arepolymerized by the living radical polymerization, and the bondingportion 31 which is formed by the living radical polymerization exhibitsthe excellent reactivity with respect to the hydroxyl group positionedon the surface of the base particle 2.

In addition, examples of one polymerizable group included in themonomers M2 include polymerizable groups having a carbon-carbon doublebond such as a vinyl group, a styryl group, and a (meth)acryloyl group.

Examples of such monomers M2 include a vinyl monomer, a vinyl estermonomer, a vinyl amide monomer, a (meth)acrylic monomer, a (meth)acrylicester monomer, a (meth)acrylamide monomer, and a styryl monomer, each ofwhich includes one alkoxysilyl group expressed by Formula (II), and morespecifically include a silane-based monomer containing a silicon atomsuch as 3-(meth)acryloxypropyl triethoxy (methoxy)silane, vinyltriethoxy (methoxy)silane, 4-vinyl butyl triethoxy (methoxy)silane,8-vinyl octyltriethoxy (methoxy)silane, 10-methacryloyloxydecyltriethoxy (methoxy)silane, and 10-acryloyloxydecyl triethoxy(methoxy)silane. In addition, these can be used alone or in combinationof two or more types thereof.

In addition, in one polymer, the number of bonding units included in thebonding portion 31 is preferably in a range of 2 to 10, and is furtherpreferably in a range of 3 to 6. When the number of bonding units islarger than the upper limit, the bonding portion 31 has low affinitywith respect to the dispersion medium as compared with the dispersionportion 32, and thus in accordance with the type of the monomer M2, thedispersibility of the electrophoretic particles 1 may be deteriorated orthe bonding portions 31 may be partially reacted with each other. Inaddition, when the number of bonding units is smaller than the lowerlimit, in accordance with the type of the monomer M2, the monomer M2cannot be sufficiently bonded to the base particle 2, and thus thedispersibility of the electrophoretic particles 1 may be deteriorated.

Further, the number of bonding units included in the bonding portion 31can be obtained by the analysis by using a general-purpose analysisapparatus such as an NMR spectrum, an IR spectrum, an elementalanalysis, and a gel permeation chromatography (GPC). Meanwhile, in thepolymer 39, the bonding portion 31 and the dispersion portion 32 arehigh-molecular weight polymers, and thus have a certain molecular weightdistribution. Accordingly, the above-described analysis result does notnecessarily correspond to all of the polymers 39, but if the number ofbonding units which is obtained by using at least one of theabove-described methods is in a range of 2 to 8, it is possible toachieve the reactivity between the polymer 39 and the base particle 2,and the dispersibility and electrophoretic properties (chargingproperties) of the electrophoretic particle 1.

The polymer 39 can be obtained by using a manufacturing method describedbelow. For example, when a reversible addition-fragmentation chaintransfer polymerization (RAFT) method described below is used, it ispossible to obtain a relatively uniform polymer. Accordingly, if 2 moleequivalents to 10 mole equivalents of the monomer M2 is added to, andpolymerized with a chain transfer agent, it is possible to set thenumber of bonding units in the bonding portion 31 to be in theabove-described range. In consideration of the aforementioneddescription, in a case where the additive rate of the monomer M2 isequal to or less than 100%, the polymerization reaction may be performedby setting the additive amount of the monomer M2 to be 2 moleequivalents to 10 mole equivalents.

Meanwhile, in a case where the bonding portion is generated after thedispersion portion 32 is generated, the dispersion portion 32 serves asthe chain transfer agent. In this case, for example, the weight-averagemolecular weight and the number average molecular weight of the polymerwhich constitute the dispersion portion 32 are obtained by using the GPCmethod, and then the additive amount of the monomer M2 may be determinedbased on the obtained result values.

With this, it is possible to reliably exhibit an effect with theconfiguration such that the electrophoretic particle 1 includes thepolymer 39, and thus the electrophoretic particle 1 has the excellentdispersibility in the electrophoretic dispersion liquid.

The electrophoretic particles 1 having the above described configurationare dispersed (suspended) in the dispersion medium (a liquid phasedispersion medium) in the electrophoretic dispersion liquid.

Dispersion Medium

In the embodiment, a material having a silicone oil as a main componentis used as the aforementioned dispersion medium. The silicone oilexhibits the excellent affinity with respect to the dispersion portion32 which is formed by the living radical polymerization performed byusing the above-described silicone macromonomer as the monomer M1, andthus is used as a dispersion medium.

With this, the effect of preventing the electrophoretic particles 1 frombeing aggregated is enhanced, and thus it is possible to prevent displayproperties of an electrophoretic display device 920 illustrated in FIG.7 from being deteriorated over time. In addition, the silicone oil doesnot have an unsaturated bond and thus is excellent in weatherresistance, and has high stability, which is an advantage.

Further, the kinetic viscosity of the silicone oil (the dispersionmedium) at a normal temperature (25° C.) is preferably equal to or lowerthan 5 cs, and is further preferably in a range of 2 cs to 4 cs. Eventhough the viscosity of the silicone oil (the dispersion medium) is inthe above-described range, if the electrophoretic particle 1 includesthe dispersion portion 32 formed by the living radical polymerizationperformed by using the silicone macromonomer as the monomer M1, theelectrophoretic particles 1 can be dispersed in the dispersion mediumwith the excellent dispersibility.

In addition, the relative permittivity of the silicone oil is preferablyin a range of 1.5 to 3, and is further preferably in a range of 1.7 to2.8. Such silicone oil is excellent in the dispersibility of theelectrophoretic particles 1, and has satisfactory electric insulation.For this reason, the silicone oil contributes to the realization of theelectrophoretic display device 920 which has small power consumption andis capable of displaying high contrast. Meanwhile, the value ofdielectric constant is a value measured at 50 Hz, and is a valueobtained by measuring the dispersion medium in which the amount ofmoisture is equal to or less than 50 ppm at a temperature of 25° C.

In addition, various additives such as a charge control agent, alubricant, a stabilizer, and various dyes which are composed ofparticles such as an electrolyte, a surfactant (anionic or cationic),metal soap, a resin material, a rubber material, oil, varnish, and acompound are added in the dispersion medium, as necessary.

Here, in the above-described electrophoretic dispersion liquid, thedispersion medium which has the silicone oil as a main component, andthe dispersion portion 32 which is formed by the living radicalpolymerization performed by using the silicone macromonomer expressed bythe above-described Formula (I) as the monomer M1 are the siloxane-basedcompounds, and thus exhibit excellent affinity. For this reason, thedispersion portion 32 included in the polymer 39 (the particle surfacetreatment agent) and the dispersion medium are interacted with eachother, and thus the electrophoretic particle 1 is expected to exhibitthe excellent dispersion ability in the electrophoretic dispersionliquid.

However, the inventors of the invention have studied and found that evenin a case where the combination of the dispersion medium and thedispersion portion 32 has the excellent affinity, the dispersibility ofthe electrophoretic particle in the electrophoretic dispersion liquid isnot improved to a desired degree.

In this regard, the silicone macromonomer expressed by theabove-described Formula (I) is typically generated by being polymerizedthrough the hydrosilylation reaction as the following Reaction formula(i). In this way, the catalyst containing the transition metal of group8 element such as Pt is included in the reaction system, and due tothis, the transition metal of group 8 element such as Pt also remains inthe electrophoretic dispersion liquid. As a result, the fact that theelectrophoretic particles 1 are aggregated with each other, and furtherthe electrophoretic particles 1 are attached to electrodes 93 and 94included in the electrophoretic display device 920 described below, andthereby the transition metal of group 8 element adversely affects thedispersibility of the electrophoretic particle in the electrophoreticdispersion liquid, is apparent by the further study by the inventors ofthe invention. In addition, the inventors have found that the aboveadverse effect can be resolved by setting the content of the transitionmetal of group 8 elements derived from the catalyst to be in a range ofgreater than 0 ppm to equal to or less than 2 ppm in the electrophoreticdispersion liquid, that is, in a state where the dispersibility of theelectrophoretic particles 1 is improved, the electrophoretic particles 1can be migrated without causing degradation or degradation with time ofthe contrast. Through the above studies, the invention has beencompleted.

[In the formula, R¹ represents a hydrogen atom or a methyl group, R²represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms,R³ represents a structure including one of an alkyl group having 1 to 6carbon atoms and an ether group of ethylene oxide or propylene oxide, R⁴represents a structure in which a methylene group is removed from theterminal on the Si side of R³, and n represents an integer of 0 orgreater.]

In addition, the catalyst containing the transition metal of group 8element such as Pt is not only used to generate the siliconemacromonomer expressed by the above-described Formula (I)(siloxane-based compound), but also used to generate the modifiedsilicone compound (the siloxane-based compound) which can be used as adispersant in a case where the dispersant is added to the dispersionmedium. Accordingly, in a case where at least one of the siloxane-basedcompounds is included in the electrophoretic dispersion liquid, with theapplication of the invention, it is possible to improve thedispersibility of the electrophoretic particle in the electrophoreticdispersion liquid by setting the content of the transition metal ofgroup 8 elements to be in a range of greater than 0 ppm to equal to orless than 2 ppm in the electrophoretic dispersion liquid.

Meanwhile, examples of the modified silicone compound which is used asthe dispersant include those expressed by the following Formula (III).

In addition, specific examples of the modified silicone compoundexpressed by the following Formula (III) include those expressed by thefollowing Formula (III-A), and the modified silicone compound expressedby the following Formula (III-A) is typically generated through thehydrosilylation reaction expressed by the following Reaction formula(iii), and in the reaction system, the catalyst containing thetransition metal of group 8 element such as Pt is included.

[In the Formula (III), at least one of A¹ to A³ each independentlyrepresents any one of a monoamine group expressed by the followingFormula (a1), a diamine group expressed by the following Formula (a2), acarbinol group expressed by the following Formula (a3), a mercapto groupexpressed by the following Formula (a4), a diol group expressed by thefollowing Formula (a5), and a carboxyl group expressed by the followingFormula (a6), and those other than A¹ to A³ represent an alkyl grouphaving 1 to 4 carbon atoms, and m and n each independently represent aninteger of 0 or greater.]

[In the Formulae (a1) to (a6), each R¹ independently represents analkylene group having 2 to 6 carbon atoms, and each of R² and R⁴independently represents an alkylene group having 1 to 6 carbon atoms.]

[In the Formula (III-A) and the Formula (iii), R¹ represents an alkylenegroup having 2 to 6 carbon atoms, R² represents an alkylene group having1 to 6 carbon atoms, R³ represents a structure in which a methylenegroup is removed from the terminal on the Si side of R¹, and m and neach independently represent an integer of 0 or greater.]

In addition, the transition metal of group 8 element may be at least oneof a period 5 element and a period 6 element without being limited toPt. The catalyst containing the transition metal of group 8 element ofthe period 5 element and the period 6 element can also be used togenerate the silicone macromonomer (the siloxane-based compound)expressed by the above-described Formula (I) and the silicone compound(the siloxane-based compound) which is the dispersant. For this reason,these metal elements may be included in the electrophoretic dispersionliquid. Here, as the catalyst, a catalyst containing at least one of Ru,Rh, and Pd other than Pt is preferably used to generate thesiloxane-based compound. For this reason, it is possible to reliablyimprove the dispersibility of the electrophoretic particle by settingthe content of the metal elements to be in a range of greater than 0 ppmto equal to or less than 2 ppm in the electrophoretic dispersion liquid.Note that, the catalyst containing at least one of Pt, Ru, Rh, and Pd isnot particularly limited, for example, Pt, Pd, a chloloplatinic acid, aWilkinson catalyst expressed by the following Formula (B1), a Trostcatalyst expressed by the following Formula (B2), and those expressed bythe following Formula (B3).

Meanwhile, the catalyst containing the transition metal of group 8element which is used to generate at least one of the siliconemacromonomer expressed by the above-described Formula (I), and thesilicone oil which is the dispersion medium may be included in theelectrophoretic dispersion liquid while maintaining the form of thecatalyst, or may be present in a state where at least one of complex andsalt which is different from the form of the catalyst. As such, even ina case where the transition metal of group 8 elements are contained inthe electrophoretic dispersion liquid in a state where both the complexand salt are formed, it is possible to reliably improve thedispersibility of the electrophoretic particle by setting the content ofthe transition metal of group 8 elements to be in a range of greaterthan 0 ppm to equal to or less than 2 ppm in the electrophoreticdispersion liquid.

In addition, the content of the transition metal of group 8 elements inthe electrophoretic dispersion liquid may be greater than 0 ppm to equalto or less than 2 ppm, but is preferably in a range of 0.01 ppm to 1.0ppm, and is further preferably in a range of 0.01 ppm to 0.5 ppm. It ispossible to reliably improve the dispersibility of the electrophoreticparticle by setting the content of the transition metal of group 8elements to be in the above-described range. Here, it takes a longperiod of time to set the content to be 0 ppm, that is, to set thecontent of the transition metal of group 8 elements in theelectrophoretic dispersion liquid to be completely zero. In contrast,the shortening of the working time to spend in the removal process canbe achieved by setting the content to be 0.01 ppm. Accordingly, it ispossible to provide the electrophoretic dispersion liquid which exhibitsboth excellent dispersion ability and electrophoretic properties, andreduces the manufacturing cost.

As described above, the electrophoretic particles 1 each of which isbonded to the polymer 39 including the bonding portion 31 and thedispersion portion 32 in the bonding portion 31 on the surface of thebase particle 2 are dispersed in the silicone oil as the dispersionmedium, and the electrophoretic dispersion liquid in which the contentof the transition metal of group 8 elements is in a range of greaterthan 0 ppm to equal to or less than 2 ppm can be manufactured as below,for example.

Method of Manufacturing Electrophoretic Dispersion Liquid

The method of manufacturing an electrophoretic dispersion liquid havingthe above-described configuration includes a generating step ofobtaining the plurality of block copolymers 39 in which the dispersionportion 32 and the bonding portion 31 are bonded to each other, aremoving step of removing the transition metal of group 8 element whichis derived from the catalyst from at least one of the block copolymer 39and the dispersion medium, a bonding step of bonding the plurality ofblock copolymers 39 to the base particle 2 and thus forming the coatedlayer 3 by the reaction between the first functional group included inthe base particle 2 and the second functional group included in thesecond monomer M2 so as to obtain the electrophoretic particle 1, and adispersing step of dispersing the obtained electrophoretic particles 1in the dispersion medium so as to obtain the electrophoretic dispersionliquid.

Note that, in the generation step, through the living radicalpolymerization performed by using a polymerization initiator, thebonding portion 31 in which the second monomers M2 having the secondfunctional group are polymerized may be formed after forming thedispersion portion 32 in which the first monomers M1 are polymerized, orthe dispersion portion 32 may be formed after forming the bondingportion 31. Here, the case where the bonding portion is formed afterforming the dispersion portion 32 will be described.

Hereinafter, each step will be described in detail.

1. First, the plurality of block copolymers 39 in which the dispersionportion 32 and the bonding portion 31 are bonded to each other aregenerated (the generation step).

1-1. First, the dispersion portion 32 in which the first monomers M1 arepolymerized is formed by the living polymerization by performed by usingthe polymerization initiator.

Examples of the living polymerization method include a living radicalpolymerization method, a living cationic polymerization method, and aliving anionic polymerization method. Among them, the living radicalpolymerization method is preferably used. When the living radicalpolymerization method is used, it is possible to simply use a reactionsolution and the like generated in the reaction system, and topolymerize the monomers M1 with satisfactory controllability of thereaction.

In addition, examples of the living radical polymerization methodinclude an atom transfer radical polymerization (ATRP) method, a radicalpolymerization (NMP) method via nitroxide, a radical polymerization(TERP) method performed by using organotellurium, and a reversibleaddition-fragmentation chain transfer polymerization (RAFT) method.Among them, the reversible addition-fragmentation chain transferpolymerization (RAFT) method is preferably used. According to thereversible addition-fragmentation chain transfer polymerization (RAFT)method, it is possible to simply polymerize the monomers M1. Further, itis possible to easily set the molecular weight distribution to be equalto or less than 1.2 in the dispersion portion 32.

The polymerization initiator (a radical polymerization initiator) is notparticularly limited; however, examples thereof include an azo initiatorsuch as 2,2′-azobisisobutyronitrile (AIBN),2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile),2,2′-azobis(2,4-dimethylvaleronitrile), dimethyl2,2′-azobis(2-methylpropionate),1,1′-azobis(cyclohexane-1-carbonitrile),2,2′-azobis[2-(2-imidazolin-2-yl) propane] dihydrochloride, and2,2′-azobis[2-(2-imidazolin-2-yl) propane], and persulfate such aspotassium persulfate, and ammonium persulfate.

In addition, in the case where the reversible addition-fragmentationchain transfer polymerization (RAFT) method is used, a chain transferagent (a RAFT agent) is used other than the polymerization initiator.The chain transfer agent is not particularly limited; however, examplesthereof include a sulfur compound having a functional group such as adithioester group, a trithiocarbamate group, a xanthate group, and adithiocarbamate group.

Specifically, examples of the chain transfer agent include a compoundexpressed by the following Formulae (1) to (7), and these may be usedalone or in combination of two or more types thereof. These compoundsare relatively easily available, and can easily perform control of thereaction, and thus are preferably used.

Among these, the chain transfer agent is preferably 2-cyano-2-propylbenzo dithioate expressed by the above-described Formula (6). With this,it is possible to more easily control the reaction.

Further, when the reversible addition-fragmentation chain transferpolymerization (RAFT) method is used, the ratio of the monomer M1, thepolymerization initiator, and the chain transfer agent is appropriatelydetermined in consideration of a polymerization degree of the dispersionportion 32 to be formed and the reactivity between compounds such as themonomer M1, and the molar ratio between the monomer M1, thepolymerization initiator, and the chain transfer agent is preferablymonomer:polymerization initiator:chain transfer agent=500 to 5:5 to0.25:1. With this, it is possible to set the length (polymerizationdegree) of the dispersion portion 32 which is obtained by polymerizingthe monomers M1 to be an appropriate size.

In addition, examples of the solvent for preparing the solution whichpolymerizes the monomers M1 by the living radical polymerization includewater, alcohol such as methanol, ethanol, and butanol, a hydrocarbonsuch as hexane, octane, benzene, toluene, and xylene, an ether such asdiethyl ether and tetrahydrofuran, an ester such as ethyl acetate andbutyl acetate, a halogenated aromatic hydrocarbon such as chlorobenzeneand o-dichlorobenzene. These may be used alone or as a mixed solvent.

In addition, it is preferable that the solution (a reaction solution) issubjected to a deoxygenation treatment before starting thepolymerization reaction. Examples of the deoxygenation treatment includesubstitution after the vacuum degassing due to an inert gas such as anargon gas and a nitrogen gas, and a purge treatment.

Further, at the time of the polymerization reaction of the monomer M1,it is possible to further rapidly and reliably perform thepolymerization reaction of the monomers by heating the solution up to acertain temperature.

The heating temperature is slightly different depending on the type ofthe monomer M1, and thus is not particularly limited; the heatingtemperature is preferably in a range of approximately 30° C. to 100° C.In addition, the heating time (reaction time) is preferably in a rangeof 3 hours to 48 hours in a case where the heating temperature is set tobe in the above-described range.

Meanwhile, when the reversible addition-fragmentation chain transferpolymerization (RAFT) method is used, a fragment of the chain transferagent which is used as one terminal (a tip end portion) of thedispersion portion 32 remains. Then, the dispersion portion 32 havingthe aforementioned fragment acts as the chain transfer agent in thereaction of polymerizing the dispersion portion 32 and the bondingportion 31 in the following step 1-2.

Meanwhile, in the embodiment, the silicone macromonomer expressed by theabove-described Formula (I) is used as the first monomer M1, and thesilicone macromonomer (the monomer M1) is generated by proceeding theReaction formula (i) by using the catalyst containing the transitionmetal of group 8 element. Due to this, the transition metal of group 8element derived from the catalyst remains in the dispersion portion 32formed by polymerizing the first monomers M1.

1-2. Next, the bonding portion 31 in which the second monomers M2 eachof which has the second functional group having the reactivity with thefirst functional group included in the base particle 2 are polymerizedis formed so as to be bonded to the dispersion portion 32.

With this, the polymer 39 configured with a block copolymer in which thedispersion portion 32 and the bonding portion 31 are bonded to eachother is generated.

In addition, in the step 1-2, before forming the bonding portion 31which uses the monomer M2, impurities such as an unreacted monomer M1 orthe solvent, and the polymerization initiator which are used in theprevious step 1-1 are removed as necessary such that the dispersionportion 32 may be subjected to a purification treatment (a removingtreatment) for isolating and purifying. With this, the obtained polymers39 become more uniform and are highly purified. The aforementionedpurification treatment is not particularly limited, and for example,examples thereof include a column chromatography method, arecrystallization method, and a re-precipitation method. These may beused alone or in combination of two or more types thereof.

In addition, as described above, when the reversibleaddition-fragmentation chain transfer polymerization (RAFT) method isused, the fragment of the chain transfer agent which is used as oneterminal of the dispersion portion 32 remains. For this reason, thebonding portion 31 having the above-described configuration is formed insuch a manner that a solution containing the dispersion portion 32, themonomer M2, and the polymerization initiator which are obtained afterthe previous step 1-1 is prepared and the living polymerization isperformed again in the aforementioned solution.

Note that, as the solvent used in the current step, the same solvent asthat used in the previous step 1-1 can be used, and it is possible toset the condition at the time of polymerizing the monomers M2 in thesolution to be the same as the condition at the time of polymerizing themonomers M1 in the solution in the previous step 1-1.

2. Next, the transition metal of group 8 element derived from thecatalyst which is used to generate the silicone macromonomer (themonomer M1) is removed from the block copolymer 39 (the removing step).

The removing of the transition metal of group 8 element is performed inthe following step 4 in such a manner that the content of the transitionmetal of group 8 elements is in a range of greater than 0 ppm to equalto or less than 2 ppm in the electrophoretic dispersion liquid at thetime of obtaining the electrophoretic dispersion liquid by dispersingthe electrophoretic particles 1 in the dispersion medium.

The method of removing the transition metal of group 8 element is notparticularly limited; however, examples thereof include a centrifugationmethod, an adsorption method, and an extracting method. These may beused alone or in combination of two or more types thereof. According tothese methods, it is possible to remove the transition metal of group 8element from the block copolymer 39 with an excellent removal rate.

Here, from the fact that the block copolymer 39 exhibits the solubilitywith respect to an organic solvent, the centrifugation method is amethod for separating and removing the transition metal of group 8element by centrifuging the solution of the block copolymer 39 which isdissolved in the aforementioned organic solvent.

In addition, the adsorption method is a method of adsorbing thetransition metal of group 8 element to an adsorbent such as silica gel,alumina, and activated carbon so as to remove the transition metal ofgroup 8 element. Note that, examples of the method of adsorbing thetransition metal of group 8 element to the adsorbent include a method ofdispersing the adsorbent in the solution of the block copolymer 39 suchthat the transition metal of group 8 element comes in contact with theadsorbent, and a method of allowing the solution of the block copolymer39 to pass through a column which is filled with the adsorbent such thatthe transition metal of group 8 element comes in contact with theadsorbent; however, the latter method is preferably used. According tothe latter method, it is possible to increase the number of cases wherethe adsorbent comes in contact with the transition metal of group 8element, and thus it is possible to further efficiently remove thetransition metal of group 8 element.

Further, the extracting method is a method which is performed in such amanner that a water-soluble metal complex is formed by bonding thetransition metal of group 8 element to a chelating agent such as anethylenediaminetetraacetic acid (EDTA), and then is phase-separated, andthereafter, the block copolymer 39 is extracted. More specifically, theextracting method is a method which is performed in such a manner that ametal complex in which the transition metal of group 8 element is bondedto the chelating agent is formed by adding the chelating agent in thesolution of the block copolymer 39, then water is added to the solutionso as to dissolve the metal complex having water-soluble properties inthe aqueous phase side, and thereafter, the block copolymer 39 dissolvedin the oil phase side is extracted.

Note that, the removing of the transition metal of group 8 elementderived from the catalyst may be performed after generating the siliconemacromonomer expressed by the above-described Formula (I) (first monomerM1) or may be performed after generating the dispersion portion 32 bypolymerizing the first monomers M1, other than the case of beingperformed after generating the block copolymer 39 as in the current step2.

Further, the removing of the transition metal of group 8 element derivedfrom the catalyst is not limited to the case where the transition metalof group 8 element is removed from the block copolymer 39 (the particlesurface treatment agent). In a case where the dispersion medium containsthe dispersant, and the catalyst containing the transition metal ofgroup 8 element is used to generate the silicone compound used as thedispersant, it is preferable that the removing of the transition metalof group 8 element is performed after generating the dispersant. Withthis, in the following step 4, it is possible to further reliably setthe content of the transition metal of group 8 elements in theelectrophoretic dispersion liquid to be in a range of greater than 0 ppmto equal to or less than 2 ppm at the time of dispersing theelectrophoretic particles 1 in the dispersion medium including thedispersant so as to obtain the electrophoretic dispersion liquid.

3. Next, the coated layer 3 is formed in such a manner that the firstfunctional group included in the base particle 2 and the plurality ofsecond functional groups in the bonding portion 31 are reacted with eachother and then are chemically bonded to each other such that theplurality of block copolymers 39 (the particle surface treatment agent)are bonded to the surface of the base particle 2 (the bonding step).

With this, it is possible to obtain the electrophoretic particle 1 inwhich at least a portion of the base particle 2 is coated with thecoated layer 3.

Examples of such a process include a dry method and a wet method asdescribed below.

Dry Method

In the dry method, first, a solution is prepared by mixing the polymer39 and the base particle 2 into a proper solvent. Here, in order toprompt hydrolysis of the alkoxysilyl group (the second functional group)included in the polymer 39, a small amount of water, acids, and basesmay be added in the solution as necessary. In addition, heating, lightirradiation, and the like may be performed as necessary.

In this case, with respect to the volume of the base particle 2, thevolume of solvent is preferably in a range of about 1% by volume toabout 20% by volume, and is further preferably in a range of about 5% byvolume to about 10% by volume. With this, it is possible to increase thenumber of cases where the polymer 39 comes in contact with the baseparticle 2, and thus it is possible to more reliably bond the bondingportion 31 onto the surface of the base particle 2.

Subsequently, the polymer 39 is adsorbed onto the surface of the baseparticle 2 with high efficiency through the dispersion performed by theultrasonic irradiation or the stirring performed by using a ball mill, abead mill, or the like, and thereafter, the solvent is removed.

Then, the electrophoretic particle 1 is obtained in such a manner thatthe alkoxysilyl group (the second functional group) is decomposed byheating the powders obtained by removing the solvent under the conditionof a temperature in a preferable range of 100° C. to 200° C. for onehour or more so as to be chemically bonded to the hydroxyl group (thefirst functional group) which is exposed to the surface of the baseparticle 2.

Next, the remaining polymers 39 which are adsorbed onto the surface ofthe base particle 2 are removed through a plurality of times of washingoperations in the solvent again by using the centrifugal separatorwithout forming the aforementioned chemical bond.

With such steps described above, it is possible to obtain a purifiedelectrophoretic particle 1.

Wet Method

In the wet method, first, a solution is prepared by mixing the polymer39 and the base particle 2 into a proper solvent. Here, in order toprompt hydrolysis of the alkoxysilyl group (the second functional group)included in the polymer 39, a small amount of water, acids, and basesmay be added in the solution as necessary. In addition, heating, lightirradiation, and the like may be performed as necessary.

In this case, with respect to the volume of the base particle 2, thevolume of solvent is preferably in a range of about 1% by volume toabout 20% by volume, and is further preferably in a range of about 5% byvolume to about 10% by volume. With this, it is possible to increase thenumber of cases where the polymer 39 comes in contact with the baseparticle 2, and thus it is possible to more reliably bond the bondingportion 31 onto the surface of the base particle 2.

Subsequently, the polymer 39 is adsorbed onto the surface of the baseparticle 2 with high efficiency through the dispersion performed by theultrasonic irradiation or the stirring performed by using a ball mill, abead mill, or the like, and thereafter, the electrophoretic particle 1is obtained in such a manner that the alkoxysilyl group (the secondfunctional group) is decomposed by heating the solution obtained fromthe above under the condition of a temperature in a preferable range of100° C. to 200° C. for one hour or more so as to be chemically bonded tothe hydroxyl group (the first functional group) which is exposed to thesurface of the base particle 2.

Next, the remaining polymers 39 which are adsorbed onto the surface ofthe base particle 2 are removed through a plurality of times of washingoperations in the solvent again by using the centrifugal separatorwithout forming the aforementioned chemical bond.

With such steps described above, it is possible to obtain the purifiedelectrophoretic particle 1.

In accordance with the types of the monomers M1 which constitutes thepolymer 39, some electrophoretic particles 1 may not be dispersed in thedispersion solvent if the electrophoretic particle 1 is dried. In such acase, it is preferable that a solvent substitution method in which thereaction solvent is gradually substituted with the dispersion solvent(the dry step is omitted) is performed at the time of the washingoperation.

Note that, as the solvent used in the current step, the same solvent asthat used in the previous step 1-1 can be used, and it is possible touse the silicone oil which is exemplified as the dispersion liquidincluded in the electrophoretic dispersion liquid.

4. Next, the electrophoretic dispersion liquid is obtained by dispersingthe obtained electrophoretic particle 1 in the dispersion medium.

In the embodiment, a material having the aforementioned silicone oil asa main component is used as the aforementioned dispersion medium.

In this case, in the previous step 2, the transition metal of group 8element derived from the catalyst which is used to generate the siliconemacromonomer (the monomer M1) is removed from the block copolymer 39.For this reason, it is possible to set the content of the transitionmetal of group 8 elements in the electrophoretic dispersion liquid whichis obtained in the step 4 to be in a range of greater than 0 ppm toequal to or less than 2 ppm, and thus it is possible to obtain theelectrophoretic dispersion liquid in which the electrophoretic particle1 exhibits both of the excellent dispersion ability and theelectrophoretic properties.

In addition, the method of dispersing the electrophoretic particle 1 inthe dispersion medium is not particularly limited; however, examplesthereof include a paint shaker method, a ball mill method, a media millmethod, an ultrasonic dispersion method, and a stirring dispersionmethod. These may be used alone or in combination of two or more typesthereof.

Meanwhile, in the case where the dispersion medium contains thedispersant, and the catalyst containing the transition metal of group 8element is used to generate the silicone compound used as thedispersant, the removing of the transition metal of group 8 element isperformed after generating the dispersant. For this reason, also in thiscase, it is possible to set the content of the transition metal of group8 elements obtained in the step 4 to be in a range of greater than 0 ppmto equal to or less than 2 ppm in the electrophoretic dispersion liquid.

With such steps described above, the electrophoretic dispersion liquidis manufactured in such a manner that the electrophoretic particles 1,in which the polymer 39 including the bonding portion 31 and thedispersion portion 32 is bonded onto the surface of the base particle 2in the bonding portion 31, are dispersed in the silicone oil which isthe dispersion medium, and the content of the transition metal of group8 elements is set to be in a range of greater than 0 ppm to equal to orless than 2 ppm. For this reason, in the electrophoretic dispersionliquid, the electrophoretic particle exhibits both of the excellentdispersion ability and the electrophoretic properties.

Second Embodiment

Next, the second embodiment of the electrophoretic particle included inthe electrophoretic dispersion liquid of the invention will bedescribed.

FIG. 3 is a longitudinal sectional view illustrating the secondembodiment the electrophoretic particle contained in the electrophoreticdispersion liquid of the invention, FIG. 4 is a diagram illustrating asiloxane-based coupling agent which is bonded onto a surface of a baseparticle of the electrophoretic particle illustrated in FIG. 3, FIG. 5is a diagram illustrating, regarding a coupling agent and a modifiedsilicone oil which are used to obtain the siloxane-based coupling agenthaving a structure Z illustrated in FIG. 4, specific examples of areactive functional group X contained in the coupling agent, and areactive functional group Y contained in the modified silicone oil, andFIG. 6A to FIG. 6F are diagrams illustrating a polarization group whichis bonded onto the surface of the electrophoretic particle illustratedin FIG. 3.

Hereinafter, the electrophoretic dispersion liquid of the secondembodiment will be described, but the description will focus on thedifferences from the electrophoretic dispersion liquid of the firstembodiment and the same matters will be omitted.

In the electrophoretic dispersion liquid of the second embodiment, asillustrated in FIG. 3, except for the configuration of the coated layer3, the coated layer 3 which is provided in the electrophoretic particle1 included in the electrophoretic dispersion liquid is the same as thecoated layer 3 provided in the electrophoretic particle 1 of the firstembodiment as illustrated in FIG. 2.

That is, in the electrophoretic particle 1 of the second embodiment,instead of the block copolymer 39, a siloxane-based coupling agent 72and a polarization group 73 are bonded to each other on the surface ofthe base particle 2 so as to form the coated layer 3.

Accordingly, in the embodiment, the siloxane-based coupling agent 72 andthe polarization group 73 constitute the particle surface treatmentagent which is used to form the electrophoretic particle 1.

Hereinafter, the siloxane-based coupling agent 72 and the polarizationgroup 73 will be described.

The siloxane-based coupling agent 72 exhibits excellent affinity withrespect to a silicone oil used as a dispersion medium which is includedin the electrophoretic dispersion liquid, and thus is provided on thesurface of the base particle 2 in the coated layer 3 so as to impart thedispersibility to the electrophoretic particle 1 in the electrophoreticdispersion liquid.

The siloxane-based coupling agent 72 is a compound having astraight-chain molecular structure which is configured to include acoupling structure in which a plurality of siloxane bonds are coupled inseries (hereinafter, referred to as a “silicone main chain”) as a mainchain, and a side chain which is bonded to the main chain while beingbonded to the surface of the base particle 2.

Specific examples of such a siloxane-based coupling agent 72 include acompound bonded onto the surface of the base particle 2 via the sidechain derived from the coupling agent, as illustrated in FIG. 4.

The siloxane-based coupling agent 72 is obtained by performingdehydration condensation reaction between a hydrolyzable group derivedfrom the coupling agent and a hydroxyl group on the surface of the baseparticle 2 which are the reactants obtained by the reaction between themodified silicone oil and the coupling agent. Such a siloxane-basedcoupling agent 72 is configured to include a structure derived from thesilicone oil and a structure derived from the coupling agent, and astructure 722 derived from the silicone oil is bonded to the baseparticle 2 via a structure 721 derived from the coupling agent. In spiteof a linear molecular structure with a long chain, the amount of bondingthe siloxane-based coupling agent 72 having such structures onto thebase particle 2 is easily controlled, and thereby it is possible torealize the electrophoretic particle 1 including the siloxane-basedcoupling agent 72 which is strictly controlled to be a desired amount.

The weight-average molecular weight of the siloxane-based coupling agent72 is preferably in a range of approximately 1000 to 100000, and isfurther preferably in a range of approximately 10000 to 60000. When theabove weight-average molecular weight is set to be in theabove-described range, the length of the molecular structure of thesiloxane-based coupling agent 72 is optimized, and thus theelectrophoretic particle 1 to which the dispersibility derived from thelinear structure with a long chain is sufficiently imparted whilesufficiently securing an area in which the polarization group 73 can beintroduced to the surface of the base particle 2.

Note that, the weight-average molecular weight of the siloxane-basedcoupling agent 72 is the weight-average molecular weight of the in termsof polystyrene, which is measured by using the gel permeationchromatography (GPC) method.

Further, n in FIG. 4 is preferably in a range of approximately 12 to1400, and is further preferably in a range of approximately 130 to 800from the same reason as that of the above-described weight-averagemolecular weight.

In addition, the structure Z in FIG. 4 is a structure obtained byreacting the reactive functional group X included in the coupling agentand the reactive functional group Y included in the silicone oil witheach other.

Examples of the reactive functional groups X and Y include thoseillustrated in FIG. 5. R in FIG. 5 represents an aliphatic hydrocarbongroup such as an alkyl group.

Meanwhile, the terminal and the side chain of the siloxane-basedcoupling agent 72 are preferably configured to include a substituentwith low polarity. With this, it is possible to further improve thedispersibility of the electrophoretic particles 1. Examples of thespecific substituent include an alkyl group.

The polarization group 73 is provided on the surface of the baseparticle 2 so as to impart the charging properties to theelectrophoretic particle 1 in the electrophoretic dispersion liquid.

The polarization group 73 is an organic group having a main skeleton,and a substituent bonded to the main skeleton.

In the polarization group 73, the electrons are maldistributed(polarized) in the main skeleton by setting at least one of conditionsfrom the type of substituents (an electron attracting group and/or anelectron donating group), and the number of bonding times and a bondingposition with respect to the main skeleton, and thus the charging stateof the electrophoretic particle 1 is controlled.

In other words, for example, in the polarization group 73 in which anelectron attractive group (electron attracting group) is bonded as asubstituent to the main skeleton on the end portion side (hereinafter,referred to as a “terminal of the main skeleton”) which is the sideopposite to the base particle 2, the electrons are maldistributed in themain skeleton on the terminal side further than the base particle 2side. When such a polarization group 73 is introduced, the base particle2 (the electrophoretic particle 1) is negatively charged.

On the other hand, in the polarization group 73 in which the electronattracting group is bonded as a substituent to the main skeleton on thebase particle 2 side, the electrons are maldistributed to the mainskeleton on the base particle 2 side further than the terminal side.When such a polarization group 73 is introduced, the base particle 2(the electrophoretic particle 1) is positively charged.

Further, in the polarization group 73 in which an electron donativegroup (the electron donating group) is bonded to the main skeleton as asubstituent, the maldistribution of the electron density which isopposite to that described above occurs, and thus when the polarizationgroup 73 in which the electron donating group is bonded to the mainskeleton on the terminal side is introduced, the base particle 2 (theelectrophoretic particle 1) is positively charged, and when thepolarization group 73 in which the electron donating group is bonded tothe main skeleton on the base particle 2 side, the base particle 2 (theelectrophoretic particle 1) is negatively charged.

In addition, as the number of substituents which are bonded to the mainskeleton is increased, the maldistribution of the electron density tendsto be increased.

It is possible to control (adjust) the base particle 2 to be in adesired charging state by properly selecting the polarization group 73in which the above-described deviation of the electron density occursand introducing the selected polarization group 73 to the surface of thebase particle 2.

The main skeleton of the polarization group 73 is preferably in a statewhere the maldistribution of the electron density easily occurs.Accordingly, the main skeleton preferably has a portion (a structure) inwhich π electrons are delocalized. With this, the electron transfer moreeasily and smoothly occurs in the main skeleton, and thus theabove-described effect is more remarkably exhibited.

The entire portion in which the π electrons are delocalized may be astructure in which conjugated double bonds are continuous in a straightline; however, at least a portion thereof has preferably a ringstructure that forms a ring shape. With this, the electron transfer moreeasily and smoothly occurs in the main skeleton.

There are various types of ring structures; however, an aromatic ring ispreferable, and a benzene ring, a naphthalene ring, a pyridine ring, apyrrole ring, a thiophene ring, an anthracene ring, a pyrene ring, aperylene ring, a pentacene ring, a tetracene ring, a chrysene ring, anazulene ring, a fluorene ring, a triphenylene ring, a phenanthrene ring,a quinoline ring, an indole ring, a pyrazine ring, an acridine ring, acarbazole ring, a furan ring, a pyran ring, a pyrimidine ring, or apyridazine ring is particularly preferable. With this, it is likely thatthe maldistribution (polarization) of the electron density occurs in thering structure, and thereby it is possible to make the maldistributionof the electron density more remarkable in the main skeleton.

Further, it is preferable that the main skeleton has a ring structure atthe terminal thereof, and the substituent is bonded to the ringstructure. With this, it is likely that maldistribution (polarization)of the electron density in the ring structure, and thereby it ispossible to make the maldistribution of the electron density moreremarkable in the main skeleton.

In the electrophoretic particle 1, the substituent is preferably anelectric attracting group or an electron donating group. With this, itis possible to more reliably charge the base particle in a positive ornegative manner.

Here, an example of a case where the main skeleton has a benzene ring atthe terminal thereof will be described below.

In this case, I: when an electron attracting group T is bonded as asubstituent to each of at least three positions of 3-position to5-position among 2-position to 6-position of the benzene ring (in FIG.6A, all of the positions in 2-position to 6-position), as illustrated inFIG. 6A, due to the existence of the electron attracting group T, theelectrons in the main skeleton is maldistributed by being attracted tothe terminal side. For this reason, the base particle 2 is negativelycharged.

II: When the electron attracting group T is bonded as a substituent toat least one position of 3-position, 4-position, and 5-position of thebenzene ring (in FIG. 6B, positions of 3-position and 4-position), asillustrated in FIG. 6B, due to the existence of the electron attractinggroup T, the electrons in the main skeleton (particularly, on thebenzene ring) are maldistributed by being attracted to the terminalside. For this reason, the base particle 2 is negatively charged.

III: When the electron attracting group T is bonded as a substituent toat least one position of 2-position and 6-position of the benzene ring(in FIG. 6C, 2-position and 6-position), as illustrated in FIG. 6C, dueto the existence of the electron attracting group T, the electrons inthe main skeleton (particularly, on the benzene ring) are maldistributedby being attracted to the base particle 2 side. For this reason, thebase particle 2 is positively charged.

IV: When an electron donating group G is bonded as a substituent to eachof at least three positions of 3-position to 5-position among 2-positionto 6-position of the benzene ring (in FIG. 6D, four positions of2-position to 5-position), as illustrated in FIG. 6D, due to theexistence of the electron donating group G, the electrons in the mainskeleton is maldistributed by being attracted to the base particle 2side. For this reason, the base particle 2 is positively charged.

V: When the electron donating group G is bonded as a substituent to atleast one position of 3-position, 4-position, and 5-position of thebenzene ring (in FIG. 6E, 4-position), as illustrated in FIG. 6E, due tothe existence of the electron donating group G, the electrons in themain skeleton (particularly, on the benzene ring) are maldistributed bybeing pushed to the base particle 2 side. For this reason, the baseparticle 2 is positively charged.

VI: When the electron donating group G is bonded as a substituent to atleast one position of 2-position and 6-position of the benzene ring (inFIG. 6F, 2-position), as illustrated in FIG. 6F, due to the existence ofthe electron donating group G, the electrons in the main skeleton(particularly, on the benzene ring) are maldistributed by being pushedto the terminal side. For this reason, the base particle 2 is negativelycharged.

Note that, the configuration II and the configuration VI, and theconfiguration III and the configuration V may be respectively combinedwith each other. With this, it is possible to make further remarkablemaldistribution of the electron density in the main skeleton(particularly, on the benzene ring).

In addition, the main skeleton may be formed of only one ring structuredescribed above, or may be formed of a structure in which a plurality ofring structures are bonded in a straight chain. Specific examples of themain skeleton having the latter structure include those expressed by thefollowing Formulae (A-1) to (A-3).

Here, In Formulae (A-1) to (A-3), n represents an integer of 1 orgreater.

Note that, in the main skeletons expressed by the above-describedFormulae (A-1) to (A-3), the substituent is preferably bonded to thering structure at the terminal, but may be bonded to the ring structuresat the position other than the terminal.

The electron attracting group T is not particularly limited as long asthe substituent tends to strongly attract (adsorb) the electrons ascompared with the hydrogen atom; however, examples thereof include ahalogen atom such as F, Cl, Br, and I, a cyano group, a nitro group, acarboxyl group, a trifluoromethyl group, a formyl group, and a sulfogroup. Among them, preferred examples of the electron attracting groupinclude at least one selected from the group consisting of the halogenatom, the cyano group, the nitro group, the carboxyl group, and thetrifluoromethyl group. These groups particularly have high function ofattracting electrons.

On the other hand, the electron donating group G is not particularlylimited as long as the substituent tends to strongly push (donate) theelectrons as compared with the hydrogen atom; however, examples thereofinclude an amino group, an alkyl group, an alkoxy group, and a hydroxylgroup. Among them, preferred examples of the electron donating groupinclude at least one type selected from the group consisting of theamino group, the alkyl group, and the alkoxy group. These groupsparticularly have a high function of pushing electrons.

An alkyl group preferably has 1 to 30 carbon atoms, and furtherpreferably has 1 to 18. An alkoxy group preferably has 1 to 30 carbonatoms, and further preferably has 1 to 18. In the alkyl group and thealkoxy group, if the number of the carbons is excessive, it is likelythat the alkyl groups and the alkoxy groups respectively aggregated, andthereby it may be difficult to adjust the charging state of the baseparticle 2 to be in a desired state.

In addition, the total number of the carbon atoms in the main skeletonis preferably in a range of 6 to 40, and is further preferably in arange of 6 to 35. If the total number of carbon atoms is excessivelysmall, it is less likely that the electrons are delocalized, and thusthe maldistribution of the electrons may be not efficiently caused. Onthe other hand, if the total number of carbon atoms in the mainskeletons is excessively large, it less likely that the polarizationgroup 73 is introduced to the surface of the base particle 2.

As described above, the polarization group 73 is preferably introducedto the surface of the base particle 2 through the covalent bond. Withthis, it is possible to reliably prevent the polarization group 73 frombeing separated from the surface of the base particle 2. For thisreason, it is possible to maintain the charging state of the baseparticle 2 for a long time of period.

It is preferable that the polarization group 73 has a structure derivedfrom the coupling agent which is bonded onto the surface of the baseparticle 2, and the ring structure is bonded to the surface of the baseparticle 2 via the structure derived from the coupling agent.

That is, as a method (an introducing method) of introducing thepolarization group 73 to the surface of the base particle 2 through thecovalent bond, a method of using the coupling agent is preferably used.examples of the method of using the coupling agent include [A] a methodof allowing the hydroxyl group on the surface of the base particle 2 andthe coupling agent having a desired polarization group 73 to be reactedwith each other, and [B] a method which is performed in such a mannerthat the hydroxyl group on the surface of the base particle 2 and thecoupling agent having a portion of the desired polarization group 73 arereacted with each other, and then a portion of the introducedpolarization group 73 and the remaining portion of the polarizationgroup 73 are reacted with each other so as to complete the desiredpolarization group 73. According to the method of using the couplingagent, it is possible to easily and reliably introduce the polarizationgroup 73 to the surface of the base particle 2 through the covalentbond.

Note that, the hydroxyl group on the surface of the base particle 2 maybe originally included in the base particle 2, or may be introduced by ahydrophilic treatment or the like. Examples of the hydrophilic treatmentmethod include a plasma treatment, a corona treatment, a surfacetreatment with a solvent, and a surface treatment with a surfactant.

Examples of the coupling agent include a silane coupling agent, atitanium coupling agent, an aluminum coupling agent, a compound having acarboxylic acid terminal, and a compound having a phosphoric acidterminal; however, particularly, the silane coupling agent is preferablyused.

With the silane coupling agent used, the siloxane bond (siloxanenetwork) is formed on the surface of the base particle 2, and thus it ispossible to more firmly bond the polarization group 73 onto the surfaceof the base particle 2. In addition, the silane coupling agent is easilyobtainable and synthesized, and is easy to handle.

Meanwhile, the method of introducing the polarization group 73 to thesurface of the base particle 2 is not particularly limited. For example,if other reactive functional groups are present, instead of the hydroxylgroup, on the surface of the base particle 2, the reactive functionalgroups and the above-described compound having the polarization group 73are reacted with each other, and thus it is possible to introduce thepolarization group 73 to the surface of the base particle 2.

Such a polarization group 73 can be introduced to a certain area otherthan the area to which the above-described siloxane-based coupling agent72 is introduced, in the surface of the base particle 2, and may beintroduced to at least a portion of the certain area. The amount of thepolarization group 73 introduced is determined depending on the desiredcharging properties of an electrophoretic particle 1. That is, theamount of the polarization group 73 introduced is adjusted such that theelectrophoretic particle 1 has desired charging properties.

In addition, in terms of the excellent dispersibility of theelectrophoretic particles 1 in the dispersion medium, the total contentof the siloxane-based coupling agent 72 and the polarization group 73 ispreferably in a range of 0.5 parts by mass to 10 parts by mass withrespect to 100 parts by mass of the base particle 2 (the base particle).

In addition, the occupancy of the area of the surface of the baseparticle 2 to which the polarization group 73 is bonded is preferablysmaller than the occupancy of the above-described area of the surface ofthe base particle 2 to which the siloxane-based coupling agent 72 isbonded. With this, it is possible to prevent (suppress) the polarizationgroup 73 from inhibiting dispersibility caused by the siloxane-basedcoupling agent 72.

In addition, the molecular weight of the polarization group 73 ispreferably smaller than the molecular weight of the siloxane-basedcoupling agent 72. With this, it is possible to prevent (suppress) thepolarization group 73 from inhibiting the dispersibility caused by thesiloxane-based coupling agent 72. Further, since the occupancy of thearea of the surface of the base particle 2 to which the siloxane-basedcoupling agent 72 is bonded can be set to be small, it is possible tosufficiently secure the area in which the polarization group can beintroduced to the surface of the base particle. For this reason, it ispossible to control the charging properties in a wide range.

According to the above-described electrophoretic particle 1, thedispersibility in the dispersion medium is improved by thesiloxane-based coupling agent 72 and it is possible to more impart thecharging properties to the polarization group 73. In addition, it ispossible to control the charging properties of the electrophoreticparticle 1 by adjusting the types of the polarization groups 73 and theintroduction amount thereof. For this reason, regardless of the type ofbase particle 2, it is possible to exhibit the desired polarity andcharging properties of the charging amount.

Here, in the electrophoretic particle 1 of the embodiment, as describedabove, the siloxane-based coupling agent 72 and the polarization group73 constitute the particle surface treatment agent which is used to formthe electrophoretic particle 1. In the particle surface treatment agent,the siloxane-based coupling agent 72 illustrated in FIG. 4 is generatedthrough the reaction expressed by the following Reaction formula (ii),and in the reaction system, the catalyst containing the transition metalof group 8 element such as Pt is included. For this reason, similar tothe electrophoretic dispersion liquid of the first embodiment, thetransition metal of group 8 element such as Pt is also present in theelectrophoretic dispersion liquid of the embodiment; however, thecontent of the transition metal of group 8 elements is set to be in arange of greater than 0 ppm to equal to or less than 2 ppm, and thus theelectrophoretic particle can be migrate with excellent electrophoreticproperties in a state where the dispersibility of the electrophoreticparticle is improved.

In addition, in the electrophoretic dispersion liquid of the embodiment,the setting the content of the transition metal of group 8 elements tobe in a range of greater than 0 ppm to equal to or less than 2 ppm canbe performed in such a manner that after generating the siloxane-basedcoupling agent 72 which is the particle surface treatment agent, thetransition metal of group 8 element included in the siloxane-basedcoupling agent 72 is removed by using the same method as that describedas the method of removing the transition metal of group 8 elements fromthe block copolymer 39 in the first embodiment.

Meanwhile, the case where the particle surface treatment agent is formedof the block copolymer 39 in the first embodiment, and is formed of thesiloxane-based coupling agent 72 in the second embodiment, and aftergenerating the particle surface treatment agents, the content of thetransition metal of group 8 elements is set to be in a range of greaterthan 0 ppm to equal to or less than 2 ppm in the electrophoreticdispersion liquid by removing the transition metal of group 8 element isdescribed; however, the type of the particle surface treatment agent isnot limited thereto as long as the particle surface treatment agent isthe siloxane-based compound, and the catalyst containing the transitionmetal of group 8 element is used to generate the siloxane-basedcompound, and the electrophoretic dispersion liquid of the invention canbe applied to the electrophoretic dispersion liquid containing theelectrophoretic particle which includes such a particle surfacetreatment agent.

Electrophoretic Display Device

Next, the electrophoretic display device (the electrophoretic device ofthe invention) to which the electrophoretic sheet of the invention isapplied will be described below.

FIG. 7 is a diagram for schematically illustrating a longitudinal crosssection of the electrophoretic display device of the embodiment, andFIGS. 8A and 8B are schematic diagrams illustrating an operatingprinciple of the electrophoretic display device illustrated in FIG. 7.Note that, in the following description, for the convenience ofexplanation, the upper side is described as “up” and the lower side isdescribed as “low” in FIG. 7 and FIG. 8A and FIG. 8B.

The electrophoretic display device 920 illustrated in FIG. 7 includes anelectrophoresis display sheet (front plane) 921, a circuit board(backplane) 922, an adhesive layer 981 which bonds the electrophoresisdisplay sheet 921 and the circuit board 922, and a sealing portion 97which air-tightly seals a gap between the electrophoresis display sheet921 and the circuit board 922.

The electrophoresis display sheet (the electrophoretic sheet of theinvention) 921 includes a substrate 912 which is provided with a flatbase portion 92 and a second electrode 94 on the lower surface of thebase portion 92, and a display layer 9400 which is provided on the lowersurface (one surface) side of the substrate 912, and is formed of apartition wall 940 formed in a matrix shape and an electrophoreticdispersion liquid 910.

On the other hand, a circuit board 922 includes a counter substrate 911which is provided with a flat base portion 91 and a plurality of firstelectrodes 93 on the upper surface of the base portion 91, a circuit(not shown) which is provided on the counter substrate 911 (the baseportion 91), and includes a switching element such as a TFT, and adriving IC (not shown) for driving the switching element.

Hereinafter, the configuration of each portion will be sequentiallydescribed.

Each of the base portion 91 and the base portion 92 is formed of asheet-like (flat) member, and has a function of supporting andprotecting each member disposed between the base portion 91 and the baseportion 92.

Each of the base portions 91 and 92 may be formed of a flexible materialor a hard material; however, the flexible material is preferably used.With the base portions 91 and 92 having flexibility, it is possible toobtain the electrophoretic display device 920 having flexibility, thatis, the electrophoretic display device 920 which is useful to constructthe electronic paper.

In addition, in a case where each of the base portions (base materiallayers) 91 and 92 has the flexibility, the base portions 91 and 92 arepreferably formed of a resin material.

The average thickness of each of the base portions 91 and 92 isappropriately set in accordance with a constituting material and anapplication. In addition, the average thickness thereof is notparticularly limited, but is preferably in a range of 20 μm to 500 μm,and is further preferably in a range of 25 μm to 250 μm.

Each of the first electrode 93 and the second electrode 94 which areformed into a layer shape (a film shape) is provided on the surface ofthe base portions 91 and 92 on the partition wall 940 side, that is, onthe upper surface of the base portion 91 and the lower surface of thebase portion 92.

If the voltage is applied across the first electrode 93 and the secondelectrode 94, an electric field is generated therebetween, and thus thegenerated electric field acts on an electrophoretic particle 95.

In the embodiment, the second electrode 94 is set to be a commonelectrode, the first electrode 93 is set to be an individual electrode(a pixel electrode which is connected to the switching element) which isdivided in a matrix shape, and a portion in which the second electrode94 and one first electrode 93 are overlapped with each other constitutesone pixel.

The constituting material of each of the electrodes 93 and 94 is notparticularly limited as long as the material substantially hasconductivity.

The average thickness of such electrodes 93 and 94 is appropriately setin accordance with a constituting material and an application. Inaddition, the average thickness thereof is not particularly limited, butis preferably in a range of 0.05 μm to 10 μm, and is further preferablyin a range of 0.05 μm to 5 μm.

Further, in each of the base portions 91 and 92, and each of theelectrodes 93 and 94, each of the base portion and the electrode (in theembodiment, the base portion 92 and the second electrode 94) which aredisposed on the display surface side has light transmittance, that is,the base portion and the electrode are substantially transparent(colorless and transparent, colored transparent, or semi-transparent).

In the electrophoresis display sheet 921, the display layer 9400 isprovided in a state of coming in contact with the lower surface of thesecond electrode 94.

The display layer 9400 is accommodated (sealed) in a plurality of pixelspaces 9401 in which the electrophoretic dispersion liquid (theelectrophoretic dispersion liquid of the invention described above) 910is defined by the partition wall 940.

The partition wall 940 is formed between the counter substrate 911 andthe substrate 912 so as to divide the pixel spaces in a matrix shape.

Examples of the constituting material of the partition wall 940 includevarious types of resin materials such as a thermoplastic resin such asan acrylic resin, a urethane resin, and an olefin resin, a thermosettingresin such as an epoxy resin, a melamine resin, and a phenolic resin.These may be used alone or in combination of two or more types thereof.

In the embodiment, the partition wall 940 is bonded to the secondelectrode 94 via an adhesive layer 982, and thus the partition wall 940is fixed onto the substrate 912.

In the embodiment, the electrophoretic dispersion liquid 910 which isaccommodated in the pixel space 9401 is formed by dispersing(suspending) two types particles (at least one type of theelectrophoretic particles 1) which are coloring particles 95 b and whiteparticles 95 a in the dispersion medium 96, and the electrophoreticdispersion liquid of the invention described above is applied thereto.

In such an electrophoretic display device 920, if the voltage is appliedacross the first electrode 93 and the second electrode 94, an electricfield is generated therebetween, and thus the coloring particles 95 band the white particles 95 a (the electrophoretic particle 1) areelectrophoretically moved toward any one of the first electrode 93 andthe second electrode 94.

In the embodiment, the positively charged white particles 95 a and thenegatively charged coloring particles (black particles) 95 b are used.That is, as the white particle 95 a, the electrophoretic particle 1 inwhich the base particle 2 is positively (plus) charged is used, and asthe coloring particle 95 b, the electrophoretic particle 1 in which thebase particle 2 is negatively (minus) charged is used.

In a case where the aforementioned electrophoretic particles 1 are used,when the first electrode 93 is set to be a negative potential, asillustrated in FIG. 8B, the coloring particles 95 b are moved to thesecond electrode 94 side so as to be collected in the second electrode94. On the other hand, the white particles 95 a are moved to the firstelectrode 93 side so as to be collected in the first electrode 93. Forthis reason, when the electrophoretic display device 920 is viewed fromabove (display surface side), the color of coloring particles 95 b canbe seen, that is, a black color can be seen.

In contrast, if the first electrode 93 is set to be a positivepotential, as illustrated in FIG. 8A, the coloring particles 95 b aremove to the first electrode 93 side so as to be collected in the firstelectrode 93. On the other hand, the white particles 95 a are moved tothe second electrode 94 side so as to be collected in the secondelectrode 94. For this reason, when the electrophoretic display device920 is viewed from the above (the display surface side), the color ofthe white particles 95 a can be seen, that is, a white color can beseen.

With such a configuration, the amount of charging the white particles 95a and the coloring particles 95 b (the electrophoretic particle 1), thepolarity of each of the electrodes 93 and 94, and the potentialdifference between electrodes 93 and 94 are appropriately set, and thusin accordance with a combination of colors of the white particles 95 aand the coloring particles 95 b, or the number of particles collectingin the electrodes 93 and 94, desired information (images) is displayedon the display surface of the electrophoretic display device 920.

In addition, a specific gravity of the electrophoretic particle 1 ispreferably set to be substantially the same as a specific gravity of thedispersion medium 96. With this, the electrophoretic particle 1 can stayat a certain position for a long period of time in the dispersion medium96 even after stopping the application of a voltage across theelectrodes 93 and 94. That is, the information displayed on theelectrophoretic display device 920 can be held for a long period oftime.

Note that, the average particle size of the electrophoretic particle 1is preferably in a range of 0.1 μm to 10 μm, and is further preferablyin a range of 0.1 μm to 7.5 μm. When the average particle size of theelectrophoretic particle 1 is set to be in the above-described range, itis possible to reliably prevent the electrophoretic particles 1 frombeing aggregated each other, and from being precipitated in thedispersion medium 96. As a result, it is possible to preferably preventthe display quality of the electrophoretic display device 920 from beingdeteriorated.

In the embodiment, the electrophoresis display sheet 921 and the circuitboard 922 are bonded to each other via the adhesive layer 981. Withthis, the electrophoresis display sheet 921 and the circuit board 922can be more reliably fixed to each other.

The average thickness of the adhesive layer 981 is not particularlylimited, but is preferably in a range of 1 μm to 30 μm, and is furtherpreferably in a range of 5 μm to 20 μm.

The sealing portion 97 is provided between the base portion 91 and thebase portion 92, and specifically, the sealing portion 97 is providedalong the edge portion of the base portion 91 and the base portion 92.The electrodes 93 and 94, the display layer 9400, and the adhesive layer981 are air-tightly sealed by the sealing portion 97. With this, it ispossible to prevent water from entering the electrophoretic displaydevice 920, and more reliably prevent the display performance of theelectrophoretic display device 920 from being deteriorated.

As the constituting material of the sealing portion 97, the samematerials as those which are exemplified as the constituting material ofthe aforementioned partition wall 940 can be used.

Electronic Apparatus

Next, the electronic apparatus of the invention will be described.

The electronic apparatus of the invention is provided with theabove-described electrophoretic display device 920.

Electronic Paper

First, an embodiment of a case where the electronic apparatus of theinvention is applied to an electronic paper will be described.

FIG. 9 is a perspective view illustrating an embodiment in a case wherethe electronic apparatus of the invention is applied to the electronicpaper.

The electronic paper 600 illustrated in FIG. 9 is provided with a mainbody 601, which is formed of a rewritable sheet having the same textureand flexibility as those of paper, and a display unit 602.

In such an electronic paper 600, the display unit 602 is formed of theabove-described electrophoretic display device 920.

Display

Next, an embodiment in a case where the electronic apparatus of theinvention is applied to the display will be described below.

FIG. 10A and FIG. 10B are diagrams illustrating an embodiment in a casewhere the electronic apparatus of the invention is applied to a display.FIG. 10A is a section view and FIG. 10B is a plane view.

A display (a display device) 800 illustrated in FIG. 10A and FIG. 10B isprovided with a main body portion 801 and the electronic paper 600 whichis detachably provided with respect to the main body portion 801.

In the main body portion 801, an insertion port 805 which can beinserted into the electronic paper 600 is formed in a side portion (theright side in FIG. 10A), and two pairs of transport rollers 802 a and802 b are provided thereinside. When the electronic paper 600 isinserted into the main body portion 801 via an insertion port 805, theelectronic paper 600 is installed on the main body portion 801 in astate being interposed between the pair of transport rollers 802 a and802 b.

In addition, a rectangular hole portion 803 is formed on the displaysurface side (the front side of the paper in FIG. 10B) of the main bodyportion 801, and a transparent glass plate 804 is fitted into the holeportion 803. With this, it is possible to visually recognize theelectronic paper 600 in a state of being installed in the main bodyportion 801 from the outside of the main body portion 801. That is, inthe display 800, a display surface is formed in such a way that theelectronic paper 600 in the state of being installed in the main bodyportion 801 is visually recognized in the transparent glass plate 804.

In addition, a terminal portion 806 is provided at a tip end portion(the left side in FIG. 10A) of the electronic paper 600 in an insertiondirection, and a socket 807 which is connected to the terminal portion806 is provided in the main body portion 801 in the state where theelectronic paper 600 is installed in the main body portion 801. Acontroller 808 and an operation unit 809 are electrically connected tothe socket 807.

In such a display 800, the electronic paper 600 is detachably installedin the main body portion 801, and can be portably used in a state ofbeing detached from the main body portion 801.

In addition, in such a display 800, the electronic paper 600 is formedof the above-described electrophoretic display device 920.

Note that, the application of the electronic apparatus of the inventionis not limited to the above description; for example, applicationexamples thereof include a television, a view finder type or a monitordirect view type video tape recorder, a car navigation device, a pager,an electronic organizer, an electronic calculator, an electronicnewspaper, a word processor, a personal computer, a workstation, atelevision telephone, a POS terminal, and a device provided with a touchpanel, and it is possible to apply the electrophoretic display device920 to the display portion of the aforementioned various electronicapparatuses.

As described above, the electrophoretic dispersion liquid, the method ofmanufacturing an electrophoretic dispersion liquid, the electrophoreticsheet, the electrophoretic device, and the electronic apparatus of theinvention are described with reference to embodiments illustrated in thedrawings; however, the invention is not limited thereto, and theconfiguration of each portion can be replaced with any otherconfiguration having the same function. In addition, other componentsmay be added to the invention.

Further, the method of manufacturing an electrophoretic dispersionliquid of the invention may additionally have one or two or more stepsfor a certain purpose.

EXAMPLES

Next, specific examples will be described below. Manufacturing ofelectrophoretic particle, preparing of electrophoretic dispersionliquid, and evaluation of electrophoretic dispersion liquid

Example 1A 1. Synthesizing of Dispersion Monomers

In a flask, 500 g of terminal hydroxyl group silicone having themolecular weight of 16,000 (“SILAPLANE FM-0426” manufactured by JNCFilter Co., Ltd.) was input and substituted with nitrogen, then 150 mLof THF was added thereto, 15 g of methacryloyl chloride was addeddropwise to a solution of 150 mL of THF, and the solution was stirredfor three hours at room temperature so as to carry out the reaction. Theobtained reaction solution was purified by using a solvent obtained bymixing hexane and chloroform as a developing solvent with a silica gelcolumn so as to remove impurities containing the transition metal ofgroup 8 elements, and thereby a silicone macromonomer was isolated.

2. Polymerizing Dispersion Portion and Bonding Portion

In the flask, 6.2 g of 2-cyano-2-propyl benzo dithioate, and 600 mg ofazobisisobutyronitrile were added into 100 g of silicone macromonomerobtained above, the mixture was substituted with nitrogen, 100 mL ofethyl acetate was added the mixture, thereafter, the mixture was heatedand stirred for one hour at 75° C., 7.2 g of 3-methacryloxypropyltriethoxy silane (manufactured by Shin-Etsu Silicones “KBE-503”) wasadded to the mixture, and then the mixture was heated and stirred againfor three hours at 75° C. so as to carry out the polymerization. Thereaction is finished by cooling the resultant up to room temperature,and then the solvent was removed so as to obtain a block copolymer.

3. Adjustment of Electrophoretic Dispersion Liquid

An electrophoretic particle was obtained in such a manner that, in theflask, 10 g of block copolymer obtained above and 60 g of titaniaparticle (“CR90” manufactured by Ishihara Sangyo Kaisha, Ltd.) wereadded to a silicone oil (“KF-96-20 cs” manufactured by Shin-EtsuChemical Co., Ltd.), the mixture was subjected to an ultrasonictreatment for one hour, and the mixture was heated and stirred for fourhours at 180° C. such that the block copolymer was bonded to theparticle. A white electrophoretic dispersion liquid was obtained byremoving unreacted block copolymer from the reacted solution, andsubstituting the silicone oil (the dispersion medium) with “KF-96-2 cs”manufactured by Shin-Etsu Chemical Co., Ltd. Meanwhile, the content ofthe transition metal of group 8 elements (Pt) in the solution which isobtained in such a manner that 2 mL of hydrofluoric acid was added to0.4 g of electrophoretic dispersion liquid, and then the mixture wassubjected to microwave decomposition at 190° C., which was measured byusing IPC-MS (an inductively coupled plasma mass spectrometer, “SPS3000”manufactured by Seiko Instruments Inc) was 1 ppm.

In addition, except that 60 g of titanium black particle (“SC13-MT”manufactured by Mitsubishi Materials Co., Ltd.) was used instead of thetitania particle, a black electrophoretic dispersion liquid was obtainedby using the same method as that in the above description. The contentof the transition metal of group 8 elements (Pt) in the solutionobtained by using the aforementioned electrophoretic dispersion liquid,which is measured by the IPC-MS was also 1 ppm.

Example 2A

In Example 2A, a black electrophoretic dispersion liquid and a whiteelectrophoretic dispersion liquid were obtained by using the same methodas that in the above-described Example 1A, except that the impuritiescontaining the transition metal of group 8 element were removed from thereaction solution obtained in the synthesizing step of the dispersionportions by performing the purification with a centrifugal separatorinstead of the silica gel column. Meanwhile, the content of thetransition metal of group 8 elements (Pt) in each solution which isobtained in such a manner that 2 mL of hydrofluoric acid was added toeach of 0.4 g of black and white electrophoretic dispersion liquids, andthen the mixture was subjected to microwave decomposition at 190° C.,which was measured by using IPC-MS was 2 ppm.

Comparative Example 1A

In Comparative Example 1A, a black electrophoretic dispersion liquid anda white electrophoretic dispersion liquid were obtained by using thesame method as that in the above-described Example 1A except foromitting the step of removing the impurities containing the transitionmetal of group 8 element from the reaction solution obtained in thesynthesizing step of the dispersion portions. Meanwhile, the content ofthe transition metal of group 8 elements (Pt) in each solution which isobtained in such a manner that 2 mL of hydrofluoric acid was added toeach of 0.4 g of black and white electrophoretic dispersion liquids, andthen the mixture was subjected to microwave decomposition at 190° C.,which was measured by using IPC-MS was 3 ppm.

Example 1B

A white electrophoretic dispersion liquid was obtained in such a mannerthat in the flask, 60 g of titania particle (“CR90” manufactured byIshihara Sangyo Kaisha, Ltd.) and a silicone oil (“KF-96-2 cs”manufactured by Shin-Etsu Chemical Co., Ltd.) were added and stirred,and then 1 wt % of siloxane-based dispersant (“KF-393” manufactured byShin-Etsu Chemical Co., Ltd.) was added with respect to the silicone oil(the dispersion medium). Meanwhile, as the siloxane-based dispersant, asolution which was purified by using a solvent obtained by mixing hexaneand chloroform in advance as a developing solvent with a silica gelcolumn so as to remove impurities containing the transition metal ofgroup 8 elements was used. Meanwhile, the content of the transitionmetal of group 8 elements (Pt) in the solution which is obtained in sucha manner that 2 mL of hydrofluoric acid was added to 0.4 g ofelectrophoretic dispersion liquid, and then the mixture was subjected tomicrowave decomposition at 190° C., which was measured by using IPC-MSwas 1 ppm.

In addition, except that 60 g of titanium black particle (“SC13-MT”manufactured by Mitsubishi Materials Co., Ltd.) was used instead of thetitania particle, a black electrophoretic dispersion liquid was obtainedby using the same method as that in the above description. The contentof the transition metal of group 8 elements (Pt) in the solutionobtained by using the aforementioned electrophoretic dispersion liquid,which is measured by the IPC-MS was also 1 ppm.

Example 2B

In Example 2B, a black electrophoretic dispersion liquid and a whiteelectrophoretic dispersion liquid were obtained by using the same methodas that in the above-described Example 1B, except that the impuritiescontaining the transition metal of group 8 element were removed from thesiloxane-based dispersant by performing the purification with acentrifugal separator instead of the silica gel column. Meanwhile, thecontent of the transition metal of group 8 elements (Pt) in eachsolution which is obtained in such a manner that 2 mL of hydrofluoricacid was added to each of 0.4 g of black and white electrophoreticdispersion liquids, and then the mixture was subjected to microwavedecomposition at 190° C., which was measured by using IPC-MS was 2 ppm.

Comparative Example 1B

In Comparative Example 1B, a black electrophoretic dispersion liquid anda white electrophoretic dispersion liquid were obtained by using thesame method as that in the above-described Example 1B except foromitting the step of removing the impurities containing the transitionmetal of group 8 element from the siloxane-based dispersant. Meanwhile,the content of the transition metal of group 8 elements (Pt) in eachsolution which is obtained in such a manner that 2 mL of hydrofluoricacid was added to each of 0.4 g of black and white electrophoreticdispersion liquids, and then the mixture was subjected to microwavedecomposition at 190° C., which was measured by using IPC-MS was 4 ppm.

Example 1C

In Example 1C, as the silicone macromonomer, a black electrophoreticdispersion liquid and a white electrophoretic dispersion liquid wereobtained by using the same method as that in the above-described Example1A, except that in the synthesizing step of the dispersion portions, thesilicone macromonomer obtained by proceeding the following Reactionformula (i-a) by using a material containing Pd as the catalyst which isexpressed in the above-described Formula (B3). Here, the hydrosilylationreaction in the following Reaction formula (i-a) were performed underthe reaction conditions of room temperature, 30 minutes, and catalystequivalent of 0.05. In addition, the content of the transition metal ofgroup 8 elements (Pd) in each solution which is obtained in such amanner that 2 mL of hydrofluoric acid was added to each of 0.4 g ofblack and white electrophoretic dispersion liquids, and then the mixturewas subjected to microwave decomposition at 190° C., which was measuredby using IPC-MS was 1 ppm.

Example 2C

In Example 2C, a black electrophoretic dispersion liquid and a whiteelectrophoretic dispersion liquid were obtained by using the same methodas that in the above-described Example 1C, except that the impuritiescontaining the transition metal of group 8 element were removed from thereaction solution obtained in the synthesizing step of the dispersionportions by performing the purification with a centrifugal separatorinstead of the silica gel column. Meanwhile, the content of thetransition metal of group 8 elements (Pd) in each solution which isobtained in such a manner that 2 mL of hydrofluoric acid was added toeach of 0.4 g of black and white electrophoretic dispersion liquids, andthen the mixture was subjected to microwave decomposition at 190° C.,which was measured by using IPC-MS was 2 ppm.

Comparative Example 1C

In Comparative Example 1C, a black electrophoretic dispersion liquid anda white electrophoretic dispersion liquid were obtained by using thesame method as that in the above-described Example 1C except foromitting the step of removing the impurities containing the transitionmetal of group 8 element from the reaction solution obtained in thesynthesizing step of the dispersion portions. Meanwhile, the content ofthe transition metal of group 8 elements (Pd) in each solution which isobtained in such a manner that 2 mL of hydrofluoric acid was added toeach of 0.4 g of black and white electrophoretic dispersion liquids, andthen the mixture was subjected to microwave decomposition at 190° C.,which was measured by using IPC-MS was 4 ppm.

Example 1D

In Example 1D, as the silicone macromonomer, a black electrophoreticdispersion liquid and a white electrophoretic dispersion liquid wereobtained by using the same method as that in the above-described Example1A, except that in the synthesizing step of the dispersion portions, thesilicone macromonomer obtained by proceeding the above-describedReaction formula (i-a) by using Trost catalyst containing Ru as thecatalyst which is expressed in the above-described Formula (B2). Here,the hydrosilylation reaction in the above-described Reaction formula(i-a) were performed under the reaction conditions of room temperature,one hour, and catalyst equivalent of 0.01. In addition, the content ofthe transition metal of group 8 elements (Ru) in each solution which isobtained in such a manner that 2 mL of hydrofluoric acid was added toeach of 0.4 g of black and white electrophoretic dispersion liquids, andthen the mixture was subjected to microwave decomposition at 190° C.,which was measured by using IPC-MS was 1 ppm.

Example 2D

In Example 2D, a black electrophoretic dispersion liquid and a whiteelectrophoretic dispersion liquid were obtained by using the same methodas that in the above-described Example 1D, except that the impuritiescontaining the transition metal of group 8 element were removed from thereaction solution obtained in the synthesizing step of the dispersionportions by performing the purification with a centrifugal separatorinstead of the silica gel column. Meanwhile, the content of thetransition metal of group 8 elements (Ru) in each solution which isobtained in such a manner that 2 mL of hydrofluoric acid was added toeach of 0.4 g of black and white electrophoretic dispersion liquids, andthen the mixture was subjected to microwave decomposition at 190° C.,which was measured by using IPC-MS was 2 ppm.

Comparative Example 1D

In Comparative Example 1D, a black electrophoretic dispersion liquid anda white electrophoretic dispersion liquid were obtained by using thesame method as that in the above-described Example 1D except foromitting the step of removing the impurities containing the transitionmetal of group 8 element from the reaction solution obtained in thesynthesizing step of the dispersion portions. Meanwhile, the content ofthe transition metal of group 8 elements (Ru) in each solution which isobtained in such a manner that 2 mL of hydrofluoric acid was added toeach of 0.4 g of black and white electrophoretic dispersion liquids, andthen the mixture was subjected to microwave decomposition at 190° C.,which was measured by using IPC-MS was 3 ppm.

Example 1E

In Example 1E, as the silicone macromonomer, a black electrophoreticdispersion liquid and a white electrophoretic dispersion liquid wereobtained by using the same method as that in the above-described Example1A, except that in the synthesizing step of the dispersion portions, thesilicone macromonomer obtained by proceeding the above-describedReaction formula (i-a) by using Wilkinson catalyst containing Rh as thecatalyst which is expressed in the above-described Formula (B1). Here,the hydrosilylation reaction in the above-described Reaction formula(i-a) were performed under the reaction conditions of room temperature,two hours, and catalyst equivalent of 0.05. In addition, the content ofthe transition metal of group 8 elements (Rh) in each solution which isobtained in such a manner that 2 mL of hydrofluoric acid was added toeach of 0.4 g of black and white electrophoretic dispersion liquids, andthen the mixture was subjected to microwave decomposition at 190° C.,which was measured by using IPC-MS was 1 ppm.

Example 2E

In Example 2E, a black electrophoretic dispersion liquid and a whiteelectrophoretic dispersion liquid were obtained by using the same methodas that in the above-described Example 1E, except that the impuritiescontaining the transition metal of group 8 element were removed from thereaction solution obtained in the synthesizing step of the dispersionportions by performing the purification with a centrifugal separatorinstead of the silica gel column. Meanwhile, the content of thetransition metal of group 8 elements (Rh) in each solution which isobtained in such a manner that 2 mL of hydrofluoric acid was added toeach of 0.4 g of black and white electrophoretic dispersion liquids, andthen the mixture was subjected to microwave decomposition at 190° C.,which was measured by using IPC-MS was 2 ppm.

Comparative Example 1E

In Comparative Example 1E, a black electrophoretic dispersion liquid anda white electrophoretic dispersion liquid were obtained by using thesame method as that in the above-described Example 1E except foromitting the step of removing the impurities containing the transitionmetal of group 8 element from the reaction solution obtained in thesynthesizing step of the dispersion portions. Meanwhile, the content ofthe transition metal of group 8 elements (Rh) in each solution which isobtained in such a manner that 2 mL of hydrofluoric acid was added toeach of 0.4 g of black and white electrophoretic dispersion liquids, andthen the mixture was subjected to microwave decomposition at 190° C.,which was measured by using IPC-MS was 4 ppm.

4. Evaluation of Electrophoretic Dispersion Liquid

Regarding the electrophoretic dispersion liquids in the respective eachExamples and Comparative Examples, particle aggregation and electrodeadhesiveness were evaluated as follows.

Evaluation of Particle Aggregation

In other words, the black electrophoretic dispersion liquid and thewhite electrophoretic dispersion liquid in the respective Examples andComparative Examples were observed at 200-fold magnification by using amicroscope.

As a result, if the aggregation of the electrophoretic particle was notrecognized in the electrophoretic dispersion liquid, and theelectrophoretic particles were almost evenly distributed in theelectrophoretic dispersion liquid without irregularity, the evaluationwas determined as A, if the aggregation of the electrophoretic particlewas slightly recognized, but the electrophoretic particles were almostevenly distributed in the electrophoretic dispersion liquid and theirregularity was almost not found, the evaluation was determined as B,and if the aggregation of the electrophoretic particle was apparentlyrecognized, and the electrophoretic particles are maldistributed in theelectrophoretic dispersion liquid with irregularity, the evaluation wasdetermined as C.

Evaluation of Electrode Adhesiveness

Two pieces of ITO deposition glass were disposed with a gap of 50 μmtherebetween, then a voltage of 15 V was applied across electrodes in astate where the white electrophoretic dispersion liquid and the blackelectrophoretic dispersion liquid of the respective Examples andComparative Examples were added dropwise in the gap, and at that time,the existence of electrophoretic particles adhered to the electrodesurface was observed at 200-fold magnification by using a microscope.

As a result, if the electrophoretic particles were not adhered onto theelectrode surface in the electrophoretic dispersion liquid, theevaluation was determined as A, if the electrophoretic particles wereslightly adhered onto the electrode surface in the electrophoreticdispersion liquid, and the adhesion of the particles on the electrodesurface was eliminated due to the application of voltage, the evaluationwas determined as B, and if the electrophoretic particles wereapparently adhered onto the electrode surface in the electrophoreticdispersion liquid, and the adhesion of the particles on the electrodesurface was not eliminated due to the application of voltage, theevaluation was determined as C.

The evaluation results are indicated in Table.

TABLE Classification of Evaluation electrophoretic Types of Amount ofions of Method of removing Particle Electrode dispersion liquidstransition metal transition metal catalyst aggregation adhesivenessExample 1A Surface bonding type Pt 1 ppm Silica gel adsorption A Amethod Example 2A Surface bonding type Pt 2 ppm Centrifugation method AB Example 1B Dispersant type Pt 1 ppm Silica gel adsorption A A methodExample 2B Dispersant type Pt 2 ppm Centrifugation method A B Example 1CSurface bonding type Pd 1 ppm Silica gel adsorption A A method Example2C Surface bonding type Pd 2 ppm Centrifugation method A B Example 1DSurface bonding type Ru 1 ppm Silica gel adsorption A A method Example2D Surface bonding type Ru 2 ppm Centrifugation method A B Example 1ESurface bonding type Rh 1 ppm Silica gel adsorption A A method Example2E Surface bonding type Rh 2 ppm Centrifugation method A B ComparativeSurface bonding type Pt 3 ppm — C C Example 1A Comparative Dispersanttype Pt 4 ppm — C C Example 1B Comparative Surface bonding type Pd 4 ppm— C C Example 1C Comparative Surface bonding type Ru 3 ppm — C C Example1D Comparative Surface bonding type Rh 4 ppm — C C Example 1E

As apparently indicated in Table, in the electrophoretic dispersionliquids of the respective Examples, the aggregation of theelectrophoretic particles in the black electrophoretic dispersion liquidand white electrophoretic dispersion liquid, and the adhesion of theelectrophoretic particles to the electrode were appropriatelysuppressed, and thus it was found that the electrophoretic particles inthe electrophoretic dispersion liquid exhibited the excellentdispersibility and the electrophoretic properties.

In contrast, in the electrophoretic dispersion liquids of the respectiveComparative Examples, since the content of the transition metal of group8 elements derived from the catalyst was equal to or greater than 2 ppm,the aggregation of the electrophoretic particles in the electrophoreticdispersion liquid, and the adhesion of the electrophoretic particles tothe electrode were recognized, and as a result, it was found that theelectrophoretic particles in the electrophoretic dispersion liquid werenot excellent in the dispersibility and the electrophoretic properties(particularly, the dispersibility).

The entire disclosure of Japanese Patent Application No. 2015-131924,filed Jun. 30, 2015 is expressly incorporated by reference herein.

What is claimed is:
 1. An electrophoretic dispersion liquid comprising:at least one type of electrophoretic particles; and a dispersion medium,wherein the content of transition metal of group 8 elements is in arange of greater than 0 ppm to equal to or less than 2 ppm in theelectrophoretic dispersion liquid.
 2. The electrophoretic dispersionliquid according to claim 1, wherein the transition metal of group 8element is derived from a catalyst which is used to generate at leastone of a particle surface treatment agent used to form theelectrophoretic particle and a dispersant added to the dispersionmedium.
 3. The electrophoretic dispersion liquid according to claim 1,wherein the transition metal of group 8 element is at least one of aperiod 5 element and a period 6 element.
 4. The electrophoreticdispersion liquid according to claim 1, wherein in the electrophoreticdispersion liquid, the transition metal of group 8 element is present ina state where at least one of a complex and salt which contain thetransition metal of group 8 element is formed.
 5. The electrophoreticdispersion liquid according to claim 1, wherein at least one of theparticle surface treatment agent and the dispersant is a siloxane-basedcompound.
 6. The electrophoretic dispersion liquid according to claim 5,wherein the siloxane-based compound is a polymer compound.
 7. Theelectrophoretic dispersion liquid according to claim 6, wherein thesiloxane-based compound which is used as the particle surface treatmentagent is a block copolymer which contains a dispersion portion which isformed by polymerizing first monomers and a bonding portion which isformed by polymerizing second monomers having a functional group, and isbonded to the electrophoretic particle when the functional group and ahydroxyl group are reacted with each other in the bonding portion, andwherein the first monomer is a silicone macromonomer expressed by thefollowing Formula (I).

[In the formula, R¹ represents a hydrogen atom or a methyl group, R²represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms,R³ represents a structure including one of an alkyl group having 1 to 6carbon atoms and an ether group of ethylene oxide or propylene oxide,and n represents an integer of 0 or greater.]
 8. The electrophoreticdispersion liquid according to claim 6, wherein the siloxane-basedcompound used as the dispersant is a modified silicone compound.
 9. Amethod of manufacturing an electrophoretic dispersion liquid whichincludes at least one type of an electrophoretic particle, and adispersion medium, the method comprising: generating a particle surfacetreatment agent which is used to form the electrophoretic particle byusing a catalyst; removing transition metal of group 8 element which isderived from the catalyst from the particle surface treatment agent;bonding the particle surface treatment agent onto a surface of a baseparticle so as to obtain the electrophoretic particle; and dispersingthe electrophoretic particles in the dispersion medium so as to obtainthe electrophoretic dispersion liquid in which the content of thetransition metal of group 8 elements derived from the catalyst is in arange of greater than 0 ppm to equal to or less than 2 ppm.
 10. A methodof manufacturing an electrophoretic dispersion liquid which includes atleast one type of an electrophoretic particle, and a dispersion medium,the method comprising: generating a dispersant which is added in thedispersion medium by using a catalyst; removing transition metal ofgroup 8 element which is derived from the catalyst from the dispersant;and dispersing the electrophoretic particles in the dispersion mediumcontaining the dispersant so as to obtain the electrophoretic dispersionliquid in which the content of the transition metal of group 8 elementsderived from the catalyst is in a range of greater than 0 ppm to equalto or less than 2 ppm.
 11. The method of manufacturing anelectrophoretic dispersion liquid according to claim 9, wherein in theremoving, a method of removing the transition metal of group 8 elementsfrom the particle surface treatment agent or the dispersant is at leastone of a centrifugation method performed by centrifugation of thetransition metal of group 8 elements, an adsorption method performed byadsorbing the transition metal of group 8 elements into an adsorbent,and an extracting method performed in such a manner that a water-solublemetal complex containing the transition metal of group 8 elements isformed and phase-separated, and then extracted.
 12. An electrophoreticsheet comprising: a substrate; and a structure body which is provided onthe substrate and accommodates the electrophoretic dispersion liquidaccording to claim
 1. 13. An electrophoretic sheet comprising: asubstrate; and a structure body which is provided on the substrate andaccommodates the electrophoretic dispersion liquid according to claim 2.14. An electrophoretic sheet comprising: a substrate; and a structurebody which is provided on the substrate and accommodates theelectrophoretic dispersion liquid according to claim
 3. 15. Anelectrophoretic sheet comprising: a substrate; and a structure bodywhich is provided on the substrate and accommodates the electrophoreticdispersion liquid according to claim
 4. 16. An electrophoretic sheetcomprising: a substrate; and a structure body which is provided on thesubstrate and accommodates the electrophoretic dispersion liquidaccording to claim
 5. 17. An electrophoretic sheet comprising: asubstrate; and a structure body which is provided on the substrate andaccommodates the electrophoretic dispersion liquid according to claim 6.18. An electrophoretic sheet comprising: a substrate; and a structurebody which is provided on the substrate and accommodates theelectrophoretic dispersion liquid according to claim
 7. 19. Anelectrophoretic device comprising the electrophoretic sheet according toclaim
 12. 20. An electronic apparatus comprising the electrophoreticdevice according to claim 19.